JP2008169442A - Method for granulating raw material to be sintered - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for granulating a raw material to be sintered, which improves the production efficiency of a sintered ore, and is suitable for producing a sintered ore that has calcium ferrite with high strength formed on the surface thereof and hematite with high reducibility in the inner part. <P>SOLUTION: The method for granulating the raw material to be sintered by the steps of granulating the material to be sintered which does not contain limestone and coke breeze, with a drum mixer, and then adding the limestone and the coke breeze to the granulated pseudo-particles to make the limestone and the coke breeze deposit on the surface of the granulated pseudo-particles, when producing the sintered ore for a blast furnace, includes adjusting the viscosity of water for granulation to 500 mPa s or higher, when granulating the material to be sintered which does not contain the limestone and the coke breeze, granulating the material, and adding the limestone and the coke breeze to the granulated pseudo-particles to make the limestone and the coke breeze deposit on the granulated pseudo-particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of granulating a raw material for producing a sintered ore used in a blast furnace (hereinafter referred to as a sintered raw material) prior to charging it into a dweroid-type sintering machine. In detail, while improving the production efficiency of sintered ore, a high-strength calcium ferrite is formed on the surface, and a sintering raw material suitable for producing sintered ore having high reducible hematite inside is produced. It relates to a granulation method.

In general, sintered ore is manufactured through a process as shown in FIG. First, various raw materials having a weight average diameter of 1.0 to 5.0 mm at 10 mm or less, such as
(a) raw materials containing CaO such as iron ore powder, limestone, dolomite,
(b) various powders collected in the steelworks,
(c) Sintered ore sieve powder,
(d) Granulation aids such as quicklime
(e) A coagulant such as powdered coke or anthracite is cut out from each hopper 2 at a predetermined ratio and charged into the drum mixer 3a. While mixing the sintering raw materials (a) to (e) in the drum mixer 3a, water 4 is added to adjust the humidity, and then granulated by the drum mixer 3b to obtain an average particle size of 3.0 to 6.0 mm. Particles (hereinafter referred to as pseudo particles). Although FIG. 7 shows an example in which two drum mixers are used, there is an example (not shown) in which mixing, humidity conditioning and granulation are performed with only one drum mixer.

  The pseudo particles are temporarily stored in the surge hopper 5, cut out by the drum feeder 6, and filled on the endless movable pallet 8 through the chute 7 at a height of 400 to 600 mm. Since the pallet 8 always moves in the direction of the arrow a, the pseudo particles filled in the pallet 8 from the chute 7 pass through the ignition furnace 9. In the ignition furnace 9, the powder coke (see (e) above) distributed on the surface layer of the pseudo particles filled in the pallet 8 is ignited.

After passing through the ignition furnace 9, the air is sucked by the exhaust fan installed below the pallet 8, so that the carbon materials distributed from the surface carbon material to the bottom layer are sequentially ignited. In this way, the coagulant in the pseudo particles filled in the pallet 8 burns, and the sintering of the pseudo particles proceeds with the combustion heat. The obtained sintered cake is crushed and sized, and sintered ore having a particle size of 5.0 mm or more is charged into a blast furnace (not shown).

  The production amount of the sintered ore thus produced is determined by the length of the dwelloid-type sintering machine 1, the width of the pallet 8, the packed bed thickness on the pallet 8, and the bulk density of pseudo particles (depending on the brand of the raw material). It depends on your needs. Moreover, when these conditions are constant, by improving the air permeability of the packed layer on the pallet 8 to shorten the sintering time, or by increasing the cold strength of the sintered cake to improve the yield. The production efficiency of sintered ore can be increased.

  Therefore, focusing on shortening the sintering time, in order to improve the air permeability of the packed bed, it is necessary to increase the strength of the pseudo particles to be filled so that the pseudo particles do not easily collapse during the sintering process. Therefore, in order to increase the strength, various raw materials must be firmly attached using a granulation aid. As a granulation aid for the sintering raw material, ie, a binder, quick lime is typically used. Recently, a method for granulating a sintering raw material using a binder having a high viscosity has been proposed. That is, as an effective means for increasing the strength of the pseudo particles that are the granulated particles, it is possible to increase the size of the pseudo particles by increasing the strength of the pseudo particles using a binder having a high viscosity.

Here, the strength σ of the granulated body which is a pseudo particle is given by the following equation (1).
σ = 6ΨS ([1-ε] / ε) (γ / D) cos θ
^{+ (3πμR 4/2) (} da / dt) ··· (1)
σ: Tensile strength of granulated material γ: Surface tension of cross-linked substance θ: Contact angle with powder μ: Viscosity of cross-linked substance S: Surface area of powder Ψ: Degree of liquid fullness (= 0.6)
ε: Porosity of granulated material D: Specific surface area equivalent diameter a: Curvature radius of cross-linking liquid Note that 6ΨS ([1-ε] / ε) (γ / D) cosθ in equation (1) is the suction pressure by capillary force ^{refers, (3πμR 4/2) (} da / dt) refers to the resistance to external force.

According to this, in order to improve the strength σ of the granulated body, a method of reducing the contact angle between the powder and the cross-linking substance (generally granulated water which is a mixed melt of water and binder), or There is a method of increasing the viscosity of the cross-linking substance (granulated water).
However, increasing the viscosity of granulated water using a high-viscosity binder so far increases the strength of the granulated particles and increases the granulated particle diameter, but powdered limestone and coke are also produced together with iron ore powder. Since it is taken into the particles, the combustion reaction and the melting reaction do not proceed smoothly. As a result, it was known that the operation results were not good. In other words, if a binder with a high viscosity (hereinafter referred to as a high viscosity binder) is used, the viscosity of the granulated water rises, and in the granulation using the granulated water with a high viscosity, the strength of the pseudo particles increases, but with iron ore. Limestone (see (a) above) and coke coke (see (e) above) are taken into the pseudo-particles, so the combustion and melting reactions do not proceed smoothly, improving the productivity of sintered ore. could not.

For example, in the techniques disclosed in Patent Documents 1 to 3, since the powder coke is taken into the pseudo particles by using a high viscosity carboxyl group or the like, the combustibility of the powder coke is deteriorated and the progress of the combustion reaction is inhibited, There was a problem in the production efficiency of sintered ore.
That is, a technique for increasing the strength of pseudo particles using a high-viscosity binder and improving the production efficiency of sintered ore has not yet been put into practical use.
JP 2002-241851 A JP 2004-76137 A JP 2004-76134 A

  The present invention does not require a new facility for producing a sintered ore with a dweroid-type sintering machine, improves the production efficiency of the sintered ore, generates high-strength calcium ferrite on the surface, Another object of the present invention is to provide a method for granulating a sintering raw material suitable for producing a sintered ore in which hematite having a high reducibility is produced.

  The inventors diligently studied a method for increasing the strength of pseudo particles and improving the production efficiency of sintered ore using a high-viscosity binder. That is, using a high-viscosity binder, increasing the pseudo particle strength and causing a problem in the combustibility of the internal powder coke means that once pseudo particles are formed, the pseudo particles are less likely to collapse. The knowledge that the most preferable pseudo-particles for sintering can be obtained if limestone, which is an auxiliary raw material, and powder coke, which is a coagulant, can be attached to the surface of the pseudo-particles (ie, the exterior). Obtained.

The present applicant possesses the technique of Patent Document 4. In this technology, limestone and coke breeze are coated on the surface of the pseudo particles to produce high-strength calcium ferrite on the surface and to obtain a sintered ore in which highly reducible hematite is produced inside. it can.
In other words, when excluding limestone and powdered coke from the pseudo particles and exteriorizing the limestone and powdered coke on the surface of the pseudoparticles, the high viscosity binder in the granulation process of the pseudoparticles of the sintered material excluding the limestone and powdered coke After that, the strength of the pseudo particles is increased, and then the exterior coating technology possessed by the applicant, that is, the powder coke necessary as a heat source during sintering and the limestone necessary for blast furnace operation are adhered to the surface of the pseudo particles By ensuring the combustion reaction and melting reaction during sintering, the production efficiency of sintered ore is increased, high strength calcium ferrite is generated on the surface, and highly reducible hematite is generated inside. Sintered ore can be obtained.

The present invention has been made based on these findings.
That is, the present invention, when producing a blast furnace sintered ore, after granulating the sintering raw material excluding limestone and powder coke with a drum mixer, granulated by adding limestone and powder coke to the granulated pseudo particles In the granulation method of the sintering raw material in which limestone and powder coke are adhered to the surface of the pseudo particles, the viscosity of the granulated water is set to 500 mPa · s or more when granulating the sintering raw material excluding limestone and powder coke. This is a method for granulating a sintered material in which limestone and powdered coke are added to the granulated pseudo particles after adjustment and granulation, and limestone and powdered coke are adhered to the granulated pseudo particles.

  According to the present invention, when manufacturing a sintered ore with a Dwytroid type sintering machine, no new equipment is required, the production efficiency of the sintered ore is improved, and high strength calcium ferrite is generated on the surface. In addition, it is possible to granulate a sintering raw material suitable for producing a sintered ore in which hematite having a high reducibility is formed inside. In addition, the present invention can solve all the harmful effects of using a high-viscosity binder at once.

The present invention will be described with reference to the drawings.
FIG. 1 is a graph showing the relationship between the reducibility of sintered ore and the gas utilization rate of a blast furnace. The reducibility of sintered ore is defined by JIS standards, and is described here as JIS-RI. The gas utilization rate η _CO of the blast furnace is a value calculated by the following equation (2).
η _CO = CO ₂ (%) / [CO (%) + CO ₂ (%)] (2)
As is clear from FIG. 1, when the reducible JIS-RI of the sintered ore increases, the gas utilization rate η _{CO of the} blast furnace increases.

FIG. 2 is a graph showing the relationship between the gas utilization rate η _CO of the blast furnace and the fuel ratio of the blast furnace. Blast furnace fuel ratio refers to the amount of coke used per ton of pig iron. As is apparent from FIG. 2, the fuel ratio decreases as the gas utilization rate η _CO of the blast furnace increases.
From these FIG. 1 and FIG. 2, it can be seen that as the JIS-RI increases, the fuel ratio decreases. The reduction in fuel ratio means a reduction in the amount of coke used, contributing to a reduction in raw material costs in blast furnace operation. In other words, if the reducible JIS-RI of sintered ore is improved, the cost reduction of blast furnace operation can be achieved.

In addition, the cold strength of the sintered ore has a great influence on the operation of the blast furnace. That is, since the sintered ore with low cold strength is easy to collapse, it is easily pulverized when charged in the blast furnace, and impairs the air permeability in the blast furnace. Therefore, a sintered ore excellent in reducibility and having a high cold strength is a sintered ore suitable for blast furnace operation.
The mineral structures that make up the sintered ore are hematite (HE), calcium ferrite (CF), calcium silicate (CS), and magnetite (MG). The tensile strength and JIS-RI of each mineral structure are as shown in Table 1. It is. As is apparent from Table 1, the mineral structure having the highest reducibility is hematite (HE), and the mineral structure having the largest tensile strength is calcium ferrite (CF).

  In order to improve both the reducibility and the cold strength of the sintered ore composed of the mineral structure shown in Table 1, calcium ferrite having a high tensile strength is formed on the surface of the sintered ore, It is necessary to produce hematite with high reducibility. According to the research by the inventors, the sintered raw material excluding limestone and powder coke is granulated while adding water with a drum mixer to form pseudo particles, and further, the limestone and powder are formed on the surface of the pseudo particles in the drum mixer. It has been found that by sintering a granulated product in which coke is adhered to water, a sintered ore in which calcium ferrite is selectively produced on the surface and hematite is selectively produced inside can be produced.

FIG. 3 is an explanatory diagram. When the sintered raw material is granulated as it is, as shown in FIG. 3 (A), the pseudo particles are mixed with an iron-based raw material, a CaO-based raw material, a SiO ₂ -based raw material, and a heat source at the same time. Therefore, the sintered ore contains four types of mineral structures: hematite (HE), calcium ferrite (CF), calcium silicate (CS), and magnetite (MG).
Therefore, as shown in FIG. 3 (B), when the granulated product is made by adhering limestone and powdered coke around the pseudo particles obtained by removing limestone and powdered coke from the sintering raw material, the structure of the obtained sintered ore is obtained. However, calcium ferrite (CF) is selectively generated on the surface and hematite (HE) is selectively generated inside.

In Patent Document 4 which is the invention of the present applicant, a granulated product is obtained by adhering limestone and powdered coke around the pseudo particles obtained by removing limestone and powdered coke from the sintered raw material. This was realized by controlling the residence time in the later drum mixer.
However, in order to make the limestone and powdered coke more effective, the portion of nuclear ore (coarse particles) + powdered ore (fine particles from coarse particles) in FIG. It has been desired to realize a stronger and larger pseudo particle portion obtained by removing the powder coke. If this can be achieved, a boundary layer where limestone and nuclear ore + fine ore will be in contact will be completed, and in this boundary layer, limestone and iron-based materials will react, and calcium ferrite (CF) will be formed reliably. It is. Further, since the powder coke is present at the outer peripheral portion of the pseudo particle, the combustibility is deteriorated and the progress of the combustion reaction is hindered, and there is no problem in the production efficiency of the sintered ore.

Therefore, the inventors used a high-viscosity binder in the process of granulating the sintered raw material excluding limestone and powdered coke into pseudo particles, and as a result, about the viscosity of the resulting granulated water and the strength of the pseudo particles investigated.
As a result, if a high viscosity binder is used and granulated water having a viscosity of 500 mPa · s or more is used, the particle size of the pseudo particles increases during the granulation process by the drum mixer, and the drum after the pseudo particles are formed. It has been found that strong pseudo particles with less decay of the pseudo particles can be obtained even in the residence in the mixer. Therefore, the viscosity of the granulated water used in the present invention is 500 mPa · s or more.

  The types of high-viscosity binders for obtaining granulated water of 500 mPa · s or higher are carboxyl group groups, and among the carboxyl groups, cellulosic thickeners (such as carboxymethyl cellulose) and gum substances (such as guar gum and gum arabic) Etc.), or a binder using water glass or bentonite as a viscosity modifier. These binders are dissolved in water and used by adjusting to a predetermined viscosity. The viscosity is adjusted by adjusting the amount of binder added.

  FIG. 4 is a graph showing an example of the relationship between the concentration and the viscosity of the binder contained in the added water during granulation. Additive A as a binder refers to quicklime, additive B refers to guar gum, and additive C refers to carboxymethylcellulose. As is clear from FIG. 4, quick increase in viscosity is small with quick lime, but with guar gum and carboxymethylcellulose, the addition of 0.3 mass% reaches almost 500 mPa · s, and the economic burden when used as a high-viscosity binder is small. In addition, the addition water | moisture content at the time of granulation of FIG. 4 is 7 mass%.

  Figures 5 (A) and 5 (B) show the viscosity of the granulated water and the sinter production efficiency (sintering time and production rate) when the viscosity is adjusted using a high-viscosity binder and used for granulation. 5 (C) and 5 (D) show the relationship between the yield of sintered ore obtained (improvement in yield indicates an increase in cold strength) and JIS-RI. As is apparent from FIG. 5, the improvement of the sintering time and the production rate is manifested at a granulated water viscosity of 500 mPa · s, which is the reason why the viscosity is set to 500 mPa · s or more in the present invention. Further, the upper limit is a viscosity of 5000 mPa · s, preferably 1000 to 4000 mPa · s.

  The high-viscosity binder used to adjust the viscosity of the granulated water is pre-added, mixed and dissolved in the water added during granulation, and the viscosity is adjusted, or the high-viscosity binder, limestone and powder coke are used. The sintered raw materials to be removed may be mixed and brought into contact with the added water during the granulation process so as to develop the viscosity. In any case, the granulated water has viscosity and can obtain the same effect.

  As shown in FIG. 6, the sintering raw materials excluding limestone and powdered coke were cut out from the hopper 2c, and a predetermined amount was charged into the drum mixer 3, and granulated by adding the high viscosity binder 10. Further, limestone and powder coke were cut out from the hoppers 2a and 2b and a predetermined amount was charged from the outlet side of the drum mixer 3. The high-viscosity binder 10 was prepared by dissolving carboxymethyl cellulose in water and adjusting the viscosity to 1000 mPa · s.

In this way, the granulated material in which the limestone and the powder coke are adhered to the surface of the pseudo particles made of the sintering raw material excluding the limestone and the powder coke is temporarily stored in the surge hopper 5 and cut out by the drum feeder 6, and the Dwytroid type Sintering was performed with the sinter 1. This is an invention example.
On the other hand, as Comparative Example 1, water and quicklime (added by 2% by mass) were used in place of the high-viscosity binder 10, and the granulated product obtained by the same method as that of the inventive example was used. 1 was charged and sintered.

In Comparative Example 2, the sintered raw material was granulated as it was without removing limestone and powder coke, and the carboxymethyl cellulose was dissolved in water and adjusted to a viscosity of 1000 mPa · s. Was used, and the obtained granulated material was charged in the Dwytroid type sintering machine 1 for sintering.
The sintering time of the inventive example was 27 minutes, the productivity was 1.78 ton / hr · m ² , and the JIS-RI was 75%. The sintering time of Comparative Example 1 was 35 minutes, the productivity was 1.4 ton / hr · m ² , and the JIS-RI was 65%. The sintering time of Comparative Example 2 was 42 minutes, the productivity was 1.0 ton / hr · m ² , and the JIS-RI was 53%.

It is a graph which shows the relationship between the reducible JIS-RI of a sintered ore, and the gas utilization rate (eta) _CO of a blast furnace. It is a graph which shows the relationship between the gas utilization rate (eta) _{CO of a} blast furnace, and a fuel ratio. It is sectional drawing which shows the example of a granulated particle and a sintered ore typically. It is a graph which shows the relationship between the density | concentration of a binder, and a viscosity. It is a graph which shows the relationship between granulated water viscosity, sintering time, production rate, yield, and JIS-RI. It is a flowchart which shows the example of the process of manufacturing a sintered ore using the sintering raw material granulated with the method of this invention. It is a flowchart which shows the example of the manufacturing process of the conventional sintered ore.

Explanation of symbols

1 Dwightroid sintering machine 2 Hopper
2a Limestone hopper
2b powder coke hopper
2c Other raw material hopper 3 Drum mixer
3a drum mixer
3b Drum mixer 4 Water 5 Surge hopper 6 Drum feeder 7 Chute 8 Pallet 9 Ignition furnace
10 High viscosity binder

Claims (1)

  When producing sintered ore for blast furnace, after granulating the sintering raw material excluding limestone and powdered coke with a drum mixer, limestone and powdered coke are added to the granulated pseudoparticles to the surface of the granulated pseudoparticles. In the granulation method of the sintered raw material for adhering limestone and powder coke, when granulating the sintered raw material excluding the limestone and powder coke, the viscosity of the granulated water is adjusted to a viscosity of 500 mPa · s or more, A method for granulating a sintered raw material, characterized in that after granulation, limestone and powder coke are added to the granulated pseudo particles, and limestone and powder coke are adhered to the granulated pseudo particles.

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