JP4490735B2 - Manufacturing method of carbonized material agglomerates - Google Patents

Description

The present invention, blast furnace, a method of manufacturing a carbonaceous material furnished agglomerated product can be used as a shaft furnace for charging raw materials such as cupola.

  The present inventors, for the purpose of using as a raw material for vertical furnaces such as blast furnaces, cupolas, etc., by hot forming a mixture of fine ore and caking coal, In this way, we have developed an agglomerate of carbonaceous material that can achieve high strength without adding a binder such as cement.

  And such a carbonaceous material agglomerated material is, for example, as shown in FIG. 1, powdered iron ore B is heated to 400 to 800 ° C. with a rotary kiln 2 and powdered carbonaceous material A having softening and melting properties. Is separately dried at a temperature of less than 250 ° C. at which softening and melting does not occur in the rotary dryer 1, and then the powdered carbon material A and the powdered iron ore B are mixed by the biaxial mixer 3 to obtain the powdered carbon material A It is disclosed that the mixture C can be produced by hot forming with a twin roll molding machine 4 with a mixture C of 250 to 550 ° C., which is a temperature at which the material melts and melts (see Patent Documents 1 and 2).

  However, even when manufactured by the above method, it has been found that when the carbonaceous material agglomerated material D is charged into a vertical furnace and heated, explosion may occur and pulverize.

JP 2001-294944 A JP 2002-146444 A

Accordingly, an object of the present invention to provide a method of manufacturing a carbonaceous material furnished agglomerated product can be reliably prevented explosion when heated in the vertical furnace.

Invention of Claim 1 is 400-800 1 or 2 types of powdered iron containing raw materials chosen from the group which consists of powdered iron ore, blast furnace dust, converter dust, electric furnace dust, and a mill scale. The powdered carbon material having soft melting property is dried at less than 250 ° C (excluding 93 ° C or less), and then the powdered iron ore and the powdered carbon material are mixed with a mixer. A mixture of 250 to 550 ° C. and a residence time of the mixture in the mixer is set to 1 min or more and 20 min, and then the mixture is hot-molded by a molding machine, so that the following formula is established: It is the manufacturing method of the carbonaceous material agglomerate characterized by manufacturing a chemical.
Formula ε _W / ε _C ≧ 0.8
Here, ε _C is obtained by arithmetically averaging the porosity distribution from the center of the carbonaceous material agglomerated material to a position at a half of the radius in a cross section passing through the center of the carbonized material agglomerated material. Ε _W is the average porosity of the carbonaceous material agglomerated material in the cross section passing through the center of the carbonaceous material agglomerated material, and calculates the porosity distribution from the position of the radius of the carbonaceous material agglomerated material to the surface. The average porosity obtained by averaging.

  "Powdered iron-containing raw material" means raw materials mainly containing iron oxide such as iron ore and iron-making dust (blast furnace dust, converter dust, electric furnace dust, mill scale, etc.), or two or more of these raw materials It is a general term for a mixture of powders. Further, the “powdered carbon material having softening and melting property” is a general term for powdery materials including at least one carbonaceous material having softening and melting property such as caking coal and SRC. 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 invention of 請 Motomeko 1, after mixing the powdered iron ore and powdered carbonaceous material, by hot molding within a predetermined period of time, can be molded remain powdery carbonaceous material is softened molten Therefore, a high-strength agglomerated material can be obtained, and the vicinity of the agglomerated material surface can be prevented from being excessively densified, and volatile matter and reducing gas generated by heating can easily be removed from the agglomerated material. Is released and reliably prevents the agglomerates from exploding .

  Hereinafter, as an embodiment of the present invention, a case where a carbonaceous material agglomerated product is used as a raw material for a blast furnace will be described in detail. The same applies to mold furnaces.

(Composition of carbon material agglomerates)
The carbonaceous material-incorporated agglomerate according to the present invention comprises, for example, a mixture of powdered iron ore as a powdered iron-containing raw material and powdered coal as a powdered carbon material, and pores in the agglomerated material. The rate distribution satisfies the following formula (1).
ε _W / ε _C ≧ 0.8 (1)
Here, ε _C was obtained by arithmetically averaging the porosity distribution from the center of the carbonaceous material agglomerated material to the position of half the radius in the cross section passing through the center of the carbonized material agglomerated material. Ε _W is an arithmetic average of the porosity distribution from the position of half the radius of the carbonaceous material agglomerated material to the surface in the cross section passing through the center of the carbonized material agglomerated material. It is the average porosity obtained by the above.

The index of ε _W / ε _C is a quantification of the degree of densification in the vicinity of the surface of the agglomerated material. As this value becomes smaller, the surface of the agglomerated material becomes densified and heated. Volatile components and reducing gas generated inside are difficult to be released out of the agglomerated material, and the internal gas pressure rises, and explosion tends to occur. The lower limit value of ε _W / ε _C is set to 0.8 based on the examples described later, but is preferably 0.9, and more preferably 1.0. The upper limit value of ε _W / ε _C is not particularly limited from the viewpoint of preventing the explosion, but if the value of ε _W / ε _C is too large, the porosity in the vicinity of the surface becomes excessively high, and agglomeration occurs. Since the abrasion resistance of the chemical compound decreases and it tends to be pulverized, it is preferably 1.5, and more preferably 1.3.

(Manufacturing method of carbonized material agglomerates)
The conceptual diagram of the manufacture flow of the carbonaceous material agglomerated material which concerns on implementation of this invention in FIG. 1 is shown. Iron ore and carbonaceous material (eg, coke powder, general coal, anthracite, oil coke, etc.) that has substantially no softening and melting property are pulverized when necessary to obtain particles of 74 μm or less. 70% powder. Of the carbon materials, carbon materials having soft melting properties (for example, caking coal, SRC, etc.) need not be made as fine as carbon materials having substantially no soft melting properties, but powdered iron ore and It is desirable to grind to about 1 mm or less in order to maintain a good mixed state with the carbonaceous material substantially not having softening and melting properties.

The powdery carbonaceous material A thus adjusted in particle size is dried by the rotary dryer 1 at a temperature of less than 250 ° C. at which the carbonaceous material A is not softened and melted to remove adhering moisture. On the other hand, the powder iron ore B is preheated to 400 to 800 ° C. in the rotary kiln 2 so that the target temperature becomes 250 to 550 ° C. when mixed with the powder carbon material A. However, when using iron-making dust (blast furnace dust, converter dust, electric furnace dust, mill scale, etc.) by replacing part of the powdered iron ore, iron-making dust burns when preheated because it contains carbon and metallic iron. Therefore, steelmaking dust is mixed and used as it is without preheating.

  For mixing the dried powdered carbon material A and the preheated powdered iron ore B, it is commonly used in this industry that can be mixed in a short time to prevent overheating of a part of the powdered carbon material A, for example A biaxial mixer 3 is used. The mixer 3 is kept warm in order to ensure the molding temperature.

  The upper limit of the residence time (holding time) of the mixture C in the mixer 3 is 20 min, preferably 16 min, and more preferably 12 min. The reason why the residence time (holding time) of the mixture C is limited as described above is as follows.

  That is, in order to estimate the melt softening / solidification state of the powdered carbonaceous material A in the mixture C in the holding state after mixing in the mixer 3, powdered coal (log MF = 2.14; where MF : Maximum fluidity [unit: ddpm]) Using a Giesera plastometer based on JIS M8801, the change over time in the fluidity was measured under the temperature rising and holding temperature conditions. The measurement results are shown in FIG. As shown in the figure, after the fluidity expression (point a), the maximum fluidity is reached after about 12 minutes (point b), and then the fluidity decreases with the lapse of the holding time, and the fluidity is almost after about 21 minutes. Completely lost (point c). Here, when the powdered coal A having a temperature of less than 250 ° C. is charged into the mixer 3 together with the powdered iron ore B heated to 400 to 800 ° C. and mixed together, the temperature of the powdered coal A is rapidly increased. Therefore, it is estimated that the same behavior as in FIG. 2 is exhibited. Therefore, the residence time (holding time) of the mixture C in the mixer 3 needs to be 20 min or less so that the powdered carbonaceous material A in the mixture C does not lose fluidity, and 16 min or less in which higher fluidity is maintained. Furthermore, it is preferable to set it to 12 minutes or less, which ensures fluidity close to the maximum fluidity. If the residence time (holding time) of the mixture C in the mixer 3 exceeds 20 minutes, the powdered carbonaceous material A loses its fluidity almost completely, and the function as a lubricant is lost. Similarly, the surface of the agglomerated material will be densified, and if it is severe, the function as a binder may be lost, and agglomeration itself may not be possible (see Comparative Examples in Examples below).

  The lower limit value of the residence time (holding time) of the mixture C in the mixer 3 is the temperature rise time until the mixed coal A reaches the holding temperature after mixing, the raw material discharge from the rotary dryer 1 and the rotary kiln 2. In consideration of giving the mixer 3 a role as a buffer that absorbs fluctuations in the difference between the speed and the molding speed by the molding machine 3, it is preferably 1 min, further 3 min, especially 5 min.

  The mixture C composed of the powdered carbon material A and the powdered iron ore B is pressure-molded into an agglomerate (briquette) D using, for example, a twin roll molding machine 4 for hot forming. Pressure molding seems to give a strength of about 500 N / piece (for a size of about 30 mm × 25 mm × 15 mm) sufficient for the agglomerate D to withstand handling from the molding machine 4 to the top loading of the blast furnace. The molding pressure is 10 kN / cm or more, preferably 20 kN / cm or more.

  The agglomerated material D formed in this way is agglomerated by the molten carbon material A having a softening and melting property entering the voids of the powdered iron ore B and acting as a lubricant. Since the molding pressure applied to the surface of D extends almost uniformly to the inside of the agglomerate D, only the vicinity of the surface is prevented from being consolidated. As a result, the porosity distribution in the agglomerate D is averaged to satisfy the relationship of the above formula (1), and the agglomerate D in which no explosion occurs during heating is obtained.

  In addition, the carbonized material A after solidification strongly connects the particles of the powdered iron ore B and has a large contact area with the powdered iron ore B, and this agglomerated material D has high strength. In addition, the reducibility is excellent.

  The mixer 3 and the molding machine 4 are hermetically sealed, and the pyrolysis gas (volatile matter) of the carbonaceous material A generated in the mixer 3 and the molding machine 4 is mainly composed of hydrocarbons. The collected gas is used as heating fuel for the rotary kiln 2 and the like.

  The agglomerated material D after molding is cooled in the bunker 5 with an inert gas, then discharged from the bunker 5 and sieved, and the powder under the sieve is returned to the mixer 3 and used as a raw material. It becomes a high strength blast furnace raw material.

  In the invention disclosed in JP-A-11-92833, a degassing step is provided in order to reduce the volatile matter remaining in the agglomerated product after molding, but in the present invention, the degassing step is not necessarily performed. do not need. Since the agglomerate according to the invention disclosed in JP-A-11-92833 is charged into a reduction furnace having a high temperature atmosphere of 1200 to 1400 ° C., explosion of the agglomerate due to rapid generation of remaining volatile matter is prevented. While the degassing step is provided for the purpose of preventing, the agglomerate produced by the method of the present invention is charged into the blast furnace and gradually heated in the blast furnace, and therefore remains. Volatile matter is also removed gradually, so agglomeration explosion is not a problem.

  FIG. 3 shows an outline of the hot forming machine used in this example. The powdered coal shown in Table 1 and the powdered iron ore shown in Table 2 are preheated to 600 to 700 ° C. in an electric furnace (not shown) at a mass ratio of 22:78, and then 400 by an oil heater. It is charged in a mixer kept at ˜500 ° C. and mixed to 400 to 500 ° C., and the holding time in the mixer is variously changed between 7 to 27 min. Using a twin roll type molding machine, the roll rotation speed is 6 rpm, Molded into an oval briquette (agglomerated product) of 30 mm × 25 mm × 15 mm at a molding pressure of 20-29 kN / cm. The briquette having a holding time of 20 min or less is referred to as an invention example, and the briquette exceeding 20 min is referred to as a comparative example.

The Giesera maximum fluidity MF of powdered coal was measured based on JIS M8801.

[Reference example]
In addition, as a reference example, the same powder iron ore and powdered coal as in the above example are used at the same mass ratio as in the above example, and corn starch as a binder is an external number relative to the total amount of powdered iron ore and powdered coal. After adding 4% by mass and mixing, in the cold using the above-mentioned twin roll type molding machine, an egg-shaped briquette (agglomerated product) of 30 mm × 25 mm × 15 mm at a roll rotation speed of 6 rpm and a molding pressure of 25 kN / cm Molded into.

(Measurement result of porosity distribution)
The briquette of the invention example having the holding time of 7 min and the briquette of the reference example are filled with resin and then divided into two parts, and the cross section is polished. In the cross section, through the center of the briquette and along the pressing direction The porosity distribution on the straight line was measured by image analysis.

  FIG. 4 shows the measurement results normalized to the relationship between the relative distance from the center of the briquette and the relative porosity. Note that the position at a relative distance of 1.0 corresponds to the briquette surface, and the relative porosity of 1.0 corresponds to an arithmetic average of measured values of the porosity from the center to the surface of the briquette.

As shown in the figure (a), in the cold-formed briquette of the reference example, the porosity (relative porosity) is the highest at the center and decreases as it approaches the surface, and the vicinity of the surface is extremely densified. I can see that The value of ε _W / ε _C is 0.668, which does not satisfy the above formula (1).

On the other hand, as shown in FIG. 5B, the briquette of the invention example shows a variation in porosity (relative porosity), but the porosity from the center toward the surface as shown in FIG. No tendency to decrease is observed, and it can be seen that the porosity is averaged in the cross section. Further, the value of ε _W / ε _C is 1.205, which satisfies the above formula (1).

(Measurement result of mass yield)
Next, in order to investigate the presence or absence of explosion when the briquette is charged in the blast furnace and heated, each of the briquette of the example (invention example + comparative example) and the reference example is 1200 ° C. in an N ₂ atmosphere for 10 min. After being held, the sample was taken out, and the ratio of the number of samples maintaining the original briquette shape was measured.

FIG. 5 shows the relationship between ε _W / ε _C and mass yield. As is apparent from the figure, in the cold-formed briquette of the reference example, ε _W / ε _C is in the range of 0.33 to 0.71, and the lump yield is less than 88% by mass.

Further, in the case of hot forming with a holding time exceeding 20 minutes in the comparative example, there are many cases where the forming itself was impossible and could not be agglomerated in the first place, and even if formed, ε _W / ε _C was 0.5 to 0.7. The mass yield is below 80% by mass.

On the other hand, in the hot-formed briquettes having a holding time of 20 min or less in the inventive example, ε _W / ε _C is in the range of 0.91 to 1.24, and the mass yield is as high as 92% by mass or more. Therefore, it is considered that there is no problem of pulverization due to explosion.

(Results of crushing strength measurement)
About the briquette of an Example (invention example + comparative example), the crushing strength in cold was measured. FIG. 6 shows the relationship between the retention time of the mixture in the mixer and the crushing strength of the briquette (carbonaceous material agglomerated material). As is clear from the figure, the crushing strength of briquettes (carbon material interior agglomerates) maintains an extremely high value of 900 to 1000 N or more in the range of the holding time of 7 to 16 min, whereas 16 min. When it exceeds 20 minutes, the strength starts to decrease to about 50 N, which is necessary and sufficient for a blast furnace charge, and when it exceeds 20 minutes, the strength further decreases and the strength for a blast furnace charge is insufficient (note that molding itself is impossible) The crushing strength was displayed as 0 N when it could not be agglomerated.

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 graph which shows a time-dependent change of the Giesera fluidity | liquidity of a powdery carbon material on temperature conditions of temperature rising + holding | maintenance. 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 the relative distance from the center of a briquette, and a relative porosity. It is a graph which shows the relationship between (epsilon) _W / (epsilon) _C and a lump yield. It is a graph which shows the relationship between the retention time of the mixture in a mixer, and the crushing strength of a carbonaceous material agglomerate.

Explanation of symbols

1: Rotary dryer 2: Rotary kiln 3: Mixer 4: Molding machine 5: Bunker A: Powdered carbon material (powdered coal)
B: Powdered iron-containing raw material (powdered iron ore)
C: Mixture D: Carbonaceous material agglomerate (briquette)

Claims (1)

One or more powdery iron-containing raw materials selected from the group consisting of powdered iron ore, blast furnace dust, converter dust, electric furnace dust, and mill scale are heated to 400 to 800 ° C., and softened and melted. the powdery carbonaceous materials below 250 ° C. with (except for 93 ° C. or less) and dried, then the said powdery carbonaceous material and the powdery iron ore with a mixture of mixture to 250 to 550 ° C. in the mixer The residence time of the mixture in the mixer is set to 1 min or more and 20 min, and then the mixture is hot-molded by a molding machine to produce a carbonaceous material agglomerate satisfying the following relationship: A method for producing a carbonized material agglomerated material.
Formula ε _W / ε _C ≧ 0.8
Here, ε _C is obtained by arithmetically averaging the porosity distribution from the center of the carbonaceous material agglomerated material to a position at a half of the radius in a cross section passing through the center of the carbonized material agglomerated material. Ε _W is the average porosity of the carbonaceous material agglomerated material in the cross section passing through the center of the carbonaceous material agglomerated material, and calculates the porosity distribution from the position of the radius of the carbonaceous material agglomerated material to the surface. The average porosity obtained by averaging.

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