JP2953308B2 - Sinter production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is prepared without the low sinter the SiO ₂ component required to increase the ratio of sintered ore in the raw materials to be charged into the blast furnace deteriorating the reduction degradation properties About the method.

[0002]

2. Description of the Related Art A general process for producing a sintered ore charged into a blast furnace is as follows. That is, first, a sintering raw material such as iron ore powder, fine coke, and limestone is granulated in a mixing granulator while adding an appropriate amount of water. The sintering raw material thus pseudo-granulated is charged into a pallet of a sintering machine, ignited from the upper portion of the sintering material packed layer, and air is sucked from the upper portion to the lower portion of the packed layer to form powder in the raw material. The sintering material is fired by burning coke sequentially from the top. After firing, the pallet is tilted to take out a fired product (called a sintered cake), crushed and cooled, and then a product having a certain particle size or more is provided as a blast furnace raw material.
The powder having a certain particle size or less (referred to as ore return) is again supplied to the sintering raw material.

In the above-mentioned sintering process, the sintering raw material particles are partially melted at a high temperature, and the melted portion mutually joins the sintering raw material particles to form a mass. This melt contains Fe ₂ O ₃ −
CaO (calcium ferrite) melt and FeO-SiO ₂
There are two types of silicate (silicate slag) melts. The calcium ferrite melt crystallizes hematite during the cooling process, and the crystallized hematite deteriorates the reducible powderability of the sintered ore. Accordingly, it is possible to improve the reduction raw powder resistance of sintered ore when brought into positively generate silicate slag, in the actual operation equal to dividend of SiO ₂ based auxiliary raw material, during the sintering raw material Measures have been taken to increase the SiO ₂ concentration.

However, in recent years, since high-quality lump ore has been depleted, an operation for increasing the ratio (sintering ratio) of sinter to blast furnace feedstock has become common. However, the sinter
Increasing the sintering ratio while keeping the SiO ₂ concentration constant increases the amount of blast furnace slag, increases the fuel requirement per unit of hot metal in the blast furnace, and hinders blast furnace operation. Sinter ore with low SiO ₂ content has become necessary.

[0005] As a method of improving the reduction powdering resistance of a sinter, there has been proposed a method of crushing an SiO ₂ -based auxiliary material to a particle size of 1 mm or less ("Iron and Steel", 68 years (1982)). 2200-2206
page). This is to increase the reaction area of the SiO ₂ -based auxiliary raw material, thereby suppressing the amount of unreacted and remaining SiO ₂ components, and reducing the SiO ₂ content of the sintered ore. However, this method requires an apparatus for crushing the SiO ₂ -based auxiliary material, which increases the cost.

For example, Japanese Patent Application Laid-Open No. Hei 2-170926 discloses a method of kneading ore containing an SiO ₂ component together with other sintering raw materials using a drum-type vibrating kneader incorporating a cylindrical rod. It has been disclosed. According to this method,
The SiO ₂ -based auxiliary material is crushed and other sintering materials and SiO ₂
The system auxiliary materials are mixed, and the crushing of the ore containing the SiO ₂ component and the mixing of the sintering materials can be performed by one mixer. However, this method also has the following disadvantages. That is, the coarse sintering raw material is crushed.
Granulation of the sintering raw material is performed by adhering fine powder around the core coarse particles, but it becomes difficult to granulate when the coarse particles which are crushed and the core decrease, and the particle size after granulation is small. Become. This decrease in the particle size after granulation deteriorates the permeability of the packed bed when the sintering material after granulation is charged into the pallet of the sintering machine, and as a result, the sintering time is prolonged and the sintering time is increased. This results in a worsening of the production rate.

[0007] Furthermore, since good-quality ores have been depleted, it is expected that fine ore containing a large amount of particles having a particle diameter of 0.5 mm or less will need to be used as a raw material for sinter.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is a sintered ore having a low SiO ₂ concentration (low SiO ₂ sintered ore) and having good reduction powdering resistance. An object of the present invention is to provide a method for producing a sintered ore without deteriorating the sintering productivity.

[0009]

The gist of the present invention resides in the following method for producing a sintered ore.

(1) A high-speed stirring blade is used to collectively mix sintering raw materials containing 30% by weight or more of particles having a particle diameter of 0.5 mm or less and having a SiO ₂ concentration of 3.0 to 4.7% by weight. And then sintering after mixing in a mixer having a built-in.

(2) The method for producing a sintered ore according to the above (1), wherein the mixture is mixed by a mixer having a built-in high-speed stirring blade and then granulated by using a rolling granulator.

In the present invention, mm representing the size of a particle is a representative diameter of a sieve, for example, particles having a particle size of 0.5 mm or less are passed under a sieve having a sieve of 0.5 mm, By 1 mm particles is meant particles that are screened below a 2 mm sieve and suspended over a 1 mm sieve.

The above-mentioned "30% by weight of particles having a particle size of 0.5 mm or less
"Includes the above," means that at the time of mixing the raw material, the raw material contains 30% by weight or more of particles having a particle size of 0.5 mm or less, and "the SiO ₂ concentration is 3.0 to 4.7% by weight". Means that the SiO ₂ concentration in the sintered ore after compounding the raw materials and sintering is 3.0 to
4.7% by weight.

The mixer having a built-in high-speed stirring blade used in the method of the present invention is a mixer in which a blade for stirring is installed in a cylindrical pan, and both the pan and the blade rotate. Machine, for example, an Erich mixer
A typical example is a mixer called (trade name). This type of mixer has a high rotation speed of the blades of several hundred rpm and does not have a compaction action, so that it is possible to perform a sufficiently uniform mixing.

It is more desirable to mix the sintering raw materials with a mixer having the above-described high-speed stirring blades and then granulate the mixture with a rolling granulator.

In the method of the present invention, the SiO ₂ concentration of the sinter is
The reason why the sintering raw material is blended so as to be 3.0 to 4.7% by weight is that if the SiO ₂ concentration is less than 3.0% by weight,
Even if the reactivity of the O ₂ component was improved, no improvement in the reducibility of the sintered ore was expected, while the SiO ₂ concentration was 4.7% by weight.
This is because if the ratio exceeds, the amount of generated melt is large and the reduction powdering resistance of the sinter becomes good, so that it is not necessary to adopt the method of the present invention. In other words, the method of the present invention targets a sintering raw material in which the SiO ₂ concentration of the sinter becomes 3.0 to 4.7% by weight so that the sintering ratio in the blast furnace charging material can be increased. It is intended to improve the reduction pulverization resistance of the low SiO ₂ sintered ore.

[0017]

Hereinafter, the method of the present invention will be described in detail. “%” Means “% by weight”.

FIG. 1 is a schematic process drawing of the method (1).
1 is a raw material layer containing sintering raw materials (including auxiliary raw materials), 2 is a mixture of iron ore fines, coke fines, limestone, serpentine powder and the like cut out from the raw material layer 1 so as to have a predetermined composition. A granulated Erich mixer. FIG. 2 is a schematic process diagram of the above-mentioned method (2). A drum mixer 3 is provided at a stage subsequent to the Eirich mixer 2.

The above-mentioned sintering raw materials are mixed by a mixer having a built-in high-speed stirring blade for the following reason.

It has been generally known that increasing the reactivity of the SiO ₂ component reduces the amount of unreacted SiO ₂ remaining in the sinter, thereby improving the resistance of the sinter to reduction powdering. and that, the present inventors have without crushing the ore containing SiO ₂ component, a result of studying on how to enhance the reactivity of the SiO ₂ component was found that ~ following is valid.

The bonding force between the particles constituting the raw material after granulation (hereinafter referred to as “pseudo particles”) is increased.

As described above, the granulation of the sintering raw material is performed by adhering fine powder (fine particles) around coarse particles (core particles) serving as nuclei, but if the bonding force between these particles is weak. Fine powder peels off due to thermal shock (drying) at the time of sintering, and the contact state between particles constituting pseudo particles deteriorates, and SiO ₂
The reaction of the components (solid phase reaction) hardly proceeds.

At the time of granulation, the amount of particles that do not become core particles or adhered powder, that is, do not contribute to granulation, is reduced.

The particles not involved in granulation are mainly particles having a particle size of 0.25 to 2.0 mm, that is, particles having an intermediate particle size (Research on Ironmaking (1976) No.288, p.10). Since such particles have a poor contact state with other particles even after granulation, the presence of such particles in a large amount deteriorates the reactivity.

The ore containing the SiO ₂ component is uniformly mixed with other sintering raw materials.

The SiO ₂ concentration of highly ores (e.g. serpentine) has a high viscosity, so it is difficult to separate from the state in which the grains are aggregated to grain units, substantially high particle comrade of SiO ₂ concentration of aggregate It tends to exhibit a state equivalent to the presence of coarse particles of a high SiO ₂ component. When the mixing is non-uniform, the reactivity of SiO ₂ is reduced.

The inventors of the present invention have studied the means for achieving the above, and have confirmed that it is effective to collectively mix the sintering raw materials with a mixer having a built-in high-speed stirring blade. As described above, a mixer with a built-in high-speed stirring blade is a type of mixer in which a blade is installed in a cylindrical pan and both the pan and the blade rotate, and a typical example is an Erich mixer. However, the present invention is also applicable to a mixer in which a stirring blade is installed in a drum mixer.

When a mixer with a built-in high-speed stirring blade is used, the water added during mixing penetrates the entire raw material by a strong mixing force, and a water film is formed on the surface of all particles regardless of the particle diameter. It becomes possible. As a result, the plasticity of the particles increases, the adhesive force of the fine powder functioning as the adhesive powder during granulation is increased, and the bonding force between the particles constituting the pseudo particles increases. That is, the above condition can be satisfied.

Further, since the water droplets are finely divided by the strong mixing force and a water film is formed on the particle surface regardless of the particle diameter, for example, in a normal granulation method using a drum mixer, the water droplet is involved in granulation. Particles with a difficult particle size of 0.25 to 2.0 mm are also plasticized and adhere to other particles.
Is also satisfied).

The strong mixing force makes it possible to separate, for example, a highly viscous serpentine powder from agglomerated particles to a particle unit, thereby promoting uniform mixing with other sintering raw materials, The uneven distribution of the SiO ₂ component due to aggregation can be eliminated (the condition is also satisfied).

The method of sintering after mixing the sintering raw materials using the above-described mixer having a built-in high-speed stirring blade is described in the above (1).
Is a method for producing sintered ore.

In order to secure a strong mixing force for obtaining the above effects, it is desirable that the rotation speed of the high-speed stirring blade be 100 rpm or more. It should be noted that a mixer having a built-in high-speed stirring blade does not have a compaction action and therefore does not crush raw material particles.

Since the mixer used in the method of the present invention has a strong mixing power, it has a high viscosity as a SiO ₂ source.
(For example, serpentine powder) is more effective. Specifically, the combination of iron ore containing almost no SiO ₂ component and the SiO ₂ -based auxiliary material produces ore containing a relatively large amount of SiO ₂ component (for example, bandka with low iron grade) as iron ore. Used, and the effect is greater than when no SiO ₂ -based auxiliary material is used. When using a secondary material with high viscosity, strong mixing force promotes uniform mixing with other sintering raw materials in the process of separating the agglomerated state of the particles of the viscous raw material into particle units. It is.

The reason that the sintering raw material contains 30% or more of particles having a particle size of 0.5 mm or less is that if the content is less than 30%, particles having a small particle size (adhesion powder) are compared with particles having a large particle size serving as a core. This is because a small amount of fine powder) can be sufficiently granulated with a normal mixer (for example, a drum mixer), and the necessity of applying the method of the present invention is small.

The invention of the above (2) is a method of mixing by a mixer having the above-described high-speed stirring blade and then granulating by using a rolling granulator. In this case, the water necessary for granulation is desirably added at the stage of mixing with a mixer having a built-in high-speed stirring blade. According to this method, the particle size of the pseudo particles (pseudo particle size) is further increased, so that the permeability of the raw material packed layer during sintering is improved, and the production rate can be further improved.

[0036] By applying the present invention a method in the production of sintered ore, it is possible to enhance the reactivity of the SiO ₂ component, reduction based powdering property even by using a low sintering material with the content of SiO ₂ Can be produced, and the sintering ratio can be increased.

[0037]

Example 1 A sintering raw material was granulated by a method according to the present invention using a mixer having a built-in high-speed stirring blade, the effect of suppressing the collapse of pseudo particles by drying, and the amount of particles not involved in granulation. The effect of reducing the particle size, that is, the effect of involving intermediate-size particles in granulation was investigated. Table 1 shows the particle size composition of the raw materials and the granulation method, and Table 2 shows the specifications of the granulator used. In Table 1, -5 mm representing the particle diameter in Tables 3 and 5 described below means particles having a particle diameter of 2 mm or less.

(A) Disintegration of pseudo particles by drying The weight ratio of particles having a particle size of 2 mm or less in the following pseudo particle size distribution survey b and the weight ratio of particles having a particle size of 2 mm or less in the following pseudo particle size distribution survey a Was evaluated by the difference of The smaller the difference, the less the pseudo-particles are disintegrated due to drying, and the better the raw material permeability during sintering.

[Pseudo-grain size distribution survey a]
After shrinking to a unit of ~ 500 g, the mixture is sieved with a hand sieve in a wet state.

[Pseudo-grain size distribution survey b] The raw material subjected to the pseudo-grain size distribution survey a is dried at 110 ° C for 2 hours and sieved.

(B) Involvement of Intermediate Particle Size Particles in Granulation From the results of the particle size distribution investigation of the particles constituting the following pseudo particles (by pseudo particle size, that is, by pseudo particles having different particle sizes), To what extent the particles of 2-1 mm, 1-0.5 mm and 0.5-0.25 mm were included in the pseudo-particles of each particle size, that is, by analyzing the distribution state in the pseudo-particles, The involvement in granulation was evaluated.

[Survey of Particle Size Distribution of Particles Constituting Pseudo Particles (by Pseudo Particle Size)] After the pseudo particle size distribution survey b, the raw materials of each pseudo particle size are decomposed into constituent particle units by washing with water and sieved.

The results of the investigation are shown in FIGS.

FIG. 3 shows the results of the investigation on the dry disintegration of the pseudo-particles. It is the difference from the ratio. It can be seen that in the examples of the present invention using the Erich mixer, the disintegration of the pseudo particles due to drying was significantly reduced as compared with the comparative example not using the Erich mixer.

FIG. 4 shows the results of an investigation on the involvement of the intermediate particle in the granulation. The intermediate particle having a particle diameter of 0.5 to 0.25 mm, 1 to 0.5 mm and 2 to 1 mm (here, “constituent particles”) FIG. 4 is a diagram showing a distribution state of each constituent particle in pseudo particles.

The abscissa indicates the particle size range of the pseudo-particles. For example, in the figure on the left (the particle size range of the constituent particles is 0.25-0.5 mm), “0.5-1” indicates that the raw material is kept wet after granulation. This represents pseudo particles having a particle size of 1 to 0.5 mm therein, which were sieved with a hand sieve, then dried at 110 ° C., and then sieved again. Also,
The abundance ratio of the constituent particles on the vertical axis means that the pseudo particles having a particle size of 1 to 0.5 mm are decomposed into constituent particle units by washing with water, and the abundance ratio of the particles having a particle size of 0.5 to 0.25 mm is sieved. .

In FIG. 4, the solid line is the present invention, the broken line is the comparative example, and the □ and Δ marks are the ratios when the particle diameter of the constituent particles matches the particle diameter of the pseudo particles, and the constituent particles exist alone. However, when not involved in granulation, △ and ▲ are the ratios in which the constituent particles are present in pseudo-particles having a larger rank by one rank, and when the constituent particles function as core particles, ○ and The mark ● indicates the ratio of the constituent particles present in the pseudo particles having a diameter of at least two ranks larger than that of the pseudo particles, and indicates that the constituent particles are functioning as adhered powder.

From the results shown in FIG. 4, it can be seen that when the Erich mixer was used (Example of the present invention), it was not used (Comparative example).
Compared with, the ratio of the constituent particles as they are was significantly reduced (comparison between the □ and ■ marks), and the constituent particle diameter was 0.5 to 0.25 mm.
In the case of 1 to 0.5 mm
It can be seen that in the case of 2 and 1 to 1 mm, those functioning as core particles are increased.

[0049]

Example 2 A sintering pot test was performed on the sintering raw materials having the compositions A to C shown in Table 3 by applying the method of the present invention, and the reduction powdering ratio (RDI) and the ventilation property during firing (JPU) were measured. Then, the effect of improving the reduction powdering resistance was investigated. The SiO ₂ component concentration was 4.5% for Formula A, 5.2% for Formula B, and 4.5% for Formula C.

The granulator used was the same as in Example 1,
The granulation method is as shown in Table 4. Table 5 shows combinations of raw material blending and granulation methods.

In the firing, the raw material after granulation is charged into a cylindrical pot having a diameter of 300 mm to a layer height of 500 mm, and a superficial air velocity of 21.8 Nm ³ /
The test was performed under a constant condition of m ² · min. The reason why the air tower wind speed was made constant is to make the firing time, which has a large effect on the quality of the sintered ore, constant. That is, the quality of the sinter was evaluated with the sintering heat pattern as a constant condition. The ignition condition was LPG 87 liters / minute for 2 minutes.
TP (Burn Through Point, highest point of exhaust gas temperature).

FIG. 5 shows the results of the investigation. From the results in FIG. 5,
When the method of the present invention is applied, the RDI is improved. In particular, if the mixture is mixed with an Erich mixer and further granulated by using a rolling granulator (Example 2 of the present invention), the RDI becomes sintered ore. Si
It can be improved to the same level as the case of using the sintering raw material of the compound B having a high O ₂ concentration (Reference Example 1), has high air permeability during firing, and can achieve high productivity and high yield. I understand.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

[Table 4]

[0057]

[Table 5]

[0058]

According to the method of the present invention, it is possible to produce a sintered ore having good reduced powdering properties even if the SiO ₂ concentration is low. By using the low SiO ₂ sintered ore obtained by the method of the present invention, stable operation of the blast furnace becomes possible even if the mixing ratio of the sintered ore is increased,
It can sufficiently cope with the depletion of high quality lump ore materials.

[Brief description of the drawings]

FIG. 1 is a view showing schematic steps of an example of the method of the present invention.

FIG. 2 is a view showing schematic steps of another example of the method of the present invention.

FIG. 3 is a graph showing the effect of the method of the present invention on the dry disintegration of pseudo particles.

FIG. 4 is a diagram showing the effect of the method of the present invention on the involvement of intermediate-size particles in granulation.

FIG. 5 is a diagram showing the effect of the method of the present invention on reduction powdering resistance of a sinter.

[Explanation of symbols]

1: Raw material tank, 2: Erich mixer, 3: drum mixer

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22B 1/16

Claims (2)

(57) [Claims] A high-speed stirring blade is used to collectively mix sintering raw materials containing 30% by weight or more of particles having a particle size of 0.5 mm or less and having a SiO ₂ concentration of 3.0 to 4.7% by weight. A method for producing a sintered ore, comprising sintering after mixing with a built-in mixer. 2. The method for producing a sintered ore according to claim 1, wherein the mixture is mixed by a mixer having a built-in high-speed stirring blade and then granulated by using a rolling granulator.