JP5058544B2 - Manufacturing method of briquette for steelmaking raw material - Google Patents

Description

  The present invention relates to a method for producing briquettes for a steelmaking raw material formed by making a by-product such as steelmaking dust generated in a steelmaking process.

  Steelmaking, such as steelmaking dust and converter dust generated in electric furnaces and converters, scales generated in hot rolling processes, slurry sludge generated in pickling processes, and dried waste acid sludge in steelmaking processes The by-products generated in the various processes are collected and used as a steelmaking raw material, and therefore, it is generally performed to form a briquette.

  FIG. 1 shows a conventional process from the manufacture of briquettes to use in an electric furnace of a steelmaking facility. Various raw materials for steelmaking dust A, converter dust B, scale C, waste acid sludge D, coke and other E Each raw material is cut out from a hopper that individually stores a certain amount by a cutting device, put into a kneader, kneaded with a binder and water added thereto, and then kneaded with a semi-rhombus-shaped recess as shown in FIG. It is pushed into a pressure molding type dumping machine composed of a pair of rollers 2 that rotate in opposite directions to form the place 1, and the kneaded product pushed into the recess 1 is hardened to make a group. The raw material that has not been solidified by the machine, the fragments of the ears 4 of the briquette 3 as shown in FIG. 3, or briquettes having a target particle size or less are separated by a classifier consisting of a vibration sieve, and the raw material under the sieve is Return to the kneader and re-assemble It is adapted to be. On the other hand, the raw material on the sieve is transported to a curing yard by a belt conveyor, naturally dried in the curing yard, and then carried into an electric furnace and put in.

  As described above, briquettes produced by a machine are broken mechanically by sieving with a classifier, falling collisions when transferring by a belt conveyor, and loading / unloading by a heavy machine at a curing yard. During curing, the briquette collapses due to expansion due to the hydration reaction between the moisture contained in the briquette and CaO and MgO in the raw material, and when the briquette is put into a steelmaking facility such as an electric furnace, the briquette is considerable. It usually breaks in proportion and contains a lot of powder. If the raw material supplied to the furnace contains a large amount of powder, it tends to cause troubles such as shelf hanging in the furnace and productivity deterioration due to worsening of gas outflow. To avoid such problems, briquettes in the curing yard Was classified by a classifier, and the raw material on the sieve was carried into a steelmaking facility (the raw material under the sieve was returned to the kneader).

In order to avoid briquetting powdering, attempts have been made to increase briquette strength. As part of this, Patent Document 1 below discloses that a kneaded material kneaded by a kneader is baked at a temperature of 800 to 1300 ° C. in a rotary kiln. It is disclosed that the material is granulated and then charged into an electric furnace.
JP 51-28516

  The present inventors classify briquettes in the curing yard, and when the return amount when returning the raw material under the sieve to the kneading machine is set to a specific ratio with respect to the total raw materials for the steel making, the strength of the briquettes is improved and the steel making facility is improved. It has been found that the powder rate of the raw material carried in decreases.

  The present invention has been made based on such knowledge, and its object is to provide a method for producing briquettes for steelmaking raw materials in which the briquette strength is improved and the powder rate of the raw materials carried into the steelmaking facilities is reduced. It is.

In the invention according to claim 1, after adding a water-soluble binder to a steelmaking raw material containing at least 10% by mass or more of CaO and kneading with a kneader, the product is formed with a pressure forming type forming machine, In the method for producing briquettes for steelmaking raw materials comprising curing, the briquettes after curing are classified, and the sieved material is returned to the kneader in the range of 10 to 40% by mass of the total raw materials of the group, and the raw materials charged into the kneader The size of the sieving and the amount under sieving are set so that the particle size composition is 65 to 85% for 0.85 mm or less, 10 to 20% for 0.85 mm to 4.75 mm, and 5 to 15% for 4.75 mm or more. It is characterized by adjusting .

  According to the method of the present invention, it is possible to significantly increase the strength and decrease the powder rate.

  In this embodiment, in the briquette manufacturing process shown in FIG. 1, after curing in the curing yard, the return amount W to the kneading machine under the sieve separated by the classifier is in the range of 10 to 40% by mass of the total raw material of the group. It is what. In order to achieve an increase in strength and a reduction in the powder rate, the return amount needs to be 10% by mass or more of the total raw material of the group. However, even if the return amount exceeds 40% by mass, the increase in strength will reach its peak. This is not preferable because the total binder amount increases, resulting in an increase in cost and a decrease in productivity.

  In a preferred embodiment, the particle size constitution of the raw material charged into the kneader is 65 to 85% for 0.85 mm or less, 10 to 20% for 0.85 to 4.75 mm, and 5 to 15% for 4.75 mm or more. To do. In addition, under the sieve just after the formation, the sieve is also returned to the kneader, but the amount is small compared to the amount W classified after curing and returned to the kneader.

Example 1
The raw materials having the composition shown in Table 1 generated in a stainless steel manufacturing plant were blended in the ratio shown in Table 2, and an aqueous solution having a lignin (resin-based water-soluble binder) concentration of 50% was added to No. 1-No. The amount shown in Fig. 9 is added, and a small amount of water is finely adjusted and further added, kneaded by a kneader with a throughput of 9 tons per hour, and manufactured by a pressure molding type dumper shown in Fig. 2. I joined together. Immediately after the formation, the sieve was classified with a vibration sieve at the 10 mm position of the classifier (first stage sieve), and the sieved material was returned to the kneader. On the other hand, the sieve was sent to a curing yard by a belt conveyor and cured naturally for 3 days. The grounds for setting the curing period to 3 days are as follows. FIG. 4 is a diagram showing the relationship between the briquette curing time and the strength obtained by the present inventors. The strength approaches 80 kgf after 72 hours from the start of curing, and is almost saturated. After curing, classification was carried out with a vibration sieve (second stage sieve) at the 10 mm position of the classifier, and the sieve was returned to the kneader. The return amount W at this time was 15 to 40% by mass of the total material of the association. The briquettes on the sieve classified by the second stage sieve were used as raw materials for the electric furnace.

  In Example 1, the particle size distribution of the raw materials charged into the kneader, the moisture (%) immediately after being formed by the clustering machine, the crushing strength after formation (kgf), the crushing strength of the briquette after curing (kgf), The specific gravity of briquettes, the powder rate (%) indicating the proportion of powder of 10 mm or less, the daily treatment amount (T / D) in the electric furnace, and the melting power intensity index were measured individually, and the results are shown in Table 3 and Table 4 shows. The melting power intensity index is obtained by setting the average value of the conventional electric energy required to melt 1 ton of raw material in an electric furnace as 100.

Example 2
The blending amount of lignin and the particle size distribution of the raw material supplied to the kneader are the ratios shown in Tables 3 and 4, and the sieves of the first and second stage classifiers are 7 mm and the return under the second stage sieves. A briquette was produced in the same manner as in Example 1 except that the amount W was 25% by mass or 30% by mass of the total mass of the group, and the briquette on the sieve was used as a raw material for the electric furnace.

  Particle size distribution of raw materials charged into the kneader in Example 2, moisture (%) immediately after forming with a clustering machine, crushing strength after forming (kgf), crushing strength of briquette after curing (kgf), The specific gravity of briquettes, the powder rate (%) indicating the proportion of powder of 10 mm or less, the daily treatment amount (T / D) in the electric furnace, and the melting power intensity index were measured individually, and the results are shown in Table 3 and Table 4 shows.

Example 3
The blending amount of lignin and the particle size distribution of the raw material supplied to the kneader are the ratios shown in Tables 3 and 4, and the sieves of the first and second stage classifiers are 5 mm, and the return amount W is the total weight of the group. A briquette was produced in the same manner as in Example 1 except that the amount was 25% by mass or 30% by mass, and a sieved briquette was used as a raw material for an electric furnace.

  Particle size distribution of raw materials put into the kneading machine in Example 3, moisture (%) immediately after forming with a clustering machine, crushing strength after forming (kgf), crushing strength of briquette after curing (kgf), The specific gravity of briquettes, the powder rate (%) indicating the proportion of powder of 10 mm or less, the daily treatment amount (T / D) in the electric furnace, and the melting power intensity index were measured individually, and the results are shown in Table 3 and Table 4 shows.

Comparative Example 1
The blending amount of the lignin and the particle size distribution of the raw material supplied to the kneader are the ratios shown in Tables 3 and 4, and the sieve of the classifier is 10 mm (there is no classification after curing). The blending amount of the lignin is: While observing the properties and productivity of briquettes, the maximum amount was added. A briquette was produced in the same manner as in Example 1 except that the return amount under the first stage sieve was changed to 3.9 to 5.1% by mass of the total raw material of the group as shown in Table 3, and the electric furnace was used as it was. Used as raw material.

  Particle size distribution of raw materials put into the kneading machine in Comparative Example 1, moisture (%) immediately after forming with a dumping machine, crushing strength after forming (kgf), crushing strength of briquette after curing (kgf), The specific gravity of briquettes, the powder rate (%) indicating the proportion of powder of 10 mm or less, the daily treatment amount (T / D) in the electric furnace, and the melting power intensity index were measured individually, and the results are shown in Table 3 and Table 4 shows.

Comparative Example 2
The blending amount of the lignin and the particle size distribution of the raw material supplied to the kneader are the ratios shown in Tables 3 and 4, and the sieves of the first and second classifiers are 10 mm and the return under the second stage sieves. A briquette was produced in the same manner as in Example 1 except that the amount was 5.4 to 9.6 wt%, and the briquette on the sieve was used as a raw material for the electric furnace. The blending amount of lignin was set to the maximum amount that could be added while checking the properties and productivity of briquettes.

  Particle size distribution of raw materials charged into the kneader in Comparative Example 2, moisture (%) immediately after forming in the clustering machine, crushing strength after forming (kgf), crushing strength of briquette after curing (kgf), The specific gravity of briquette, the ratio of the powder ratio indicating the ratio of powder of 10 mm or less (%), the daily treatment amount in the electric furnace (T / D), and the melting power intensity index are individually measured, and the results are shown in Table 3 and Table 4.

  As shown in Table 3 and Table 4, in Examples 1 to 3, the binder basic unit increased by about 20% at maximum compared to Comparative Examples 1 and 2, and the strength after the formation, especially the strength after curing. However, the moisture content of the briquette after the formation was reduced and the powder percentage% of 10 mm or less was significantly reduced. This is because the sieving after curing that returns to the kneading machine becomes an aggregate when kneading and forming, and the binder contained in the sieving after curing is well used as a raw material because the moisture is reduced. This is due to the increase in the total amount of binder that can be added without being affected by the amount of binder contained under the sieve, as the binder added to the material accelerates the solidification reaction of the raw material, and the newly added binder in the kneader due to the decrease in moisture it is conceivable that.

  The moisture content of the briquettes after curing in Examples 1 to 3 (the briquettes after curing are usually reduced by about 2-3% from the moisture content immediately after the formation shown in Table 3) and the powder rate are reduced. From this, it is possible to suppress briquette shelves and blow-ups in the electric furnace, the processing amount can be increased as compared with Comparative Examples 1 and 2, and low energy melting in the electric furnace is possible and efficiency is improved. Processing became possible. The following can be considered as the reason why melting at low energy in an electric furnace is possible. As the raw material charged into the electric furnace descends in the furnace, it is preheated and melted by gas, but the briquettes of Examples 1 to 3 have a lower powder rate than the briquettes of Comparative Examples 1 and 2. In addition, it is considered that the outgassing becomes good and the heat transfer to the briquette is improved due to the high specific gravity, thereby reducing the energy required to dissolve the briquette.

The figure which shows the conventional briquette manufacturing process. Sectional drawing of the roller which comprises a dumpling machine. The expanded sectional view of the briquette provided with the ear | edge part after a team. The figure which shows the relationship between the curing time of briquette and intensity | strength.

Explanation of symbols

1 .. Recess 2. Roller 3. Briquette 4. Ear

Claims (1)

For steelmaking raw materials, comprising adding a water-soluble binder to a steelmaking raw material containing at least 10% by mass of CaO and kneading with a kneader, then forming with a pressure forming type forming machine and then curing. In the briquette manufacturing method, the cured briquette is classified, and the sieved material is returned to the kneader in the range of 10 to 40% by mass of the total raw material of the group , and the particle size constitution of the kneader input raw material is 0.85 mm. Steelmaking characterized by adjusting the sieve size and the amount of sieving so that the following is 65 to 85%, 0.85 mm to 4.75 mm is 10 to 20%, and 4.75 mm or more is 5 to 15%. A method for manufacturing raw material briquettes.

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