JP2000192153A - Sintered ore and production thereof, and operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered ore and a producing method thereof, with which the calorific power of generating gas in a blast furnace can be controlled without depending on the fuel ratio in the blast furnace, and an operating method of the blast furnace. SOLUTION: SiO2 content in a blending raw material is adjusted to <=6 wt.% and a prescribed quantity of solid fuel (A) adjusted to 1-10 mm grain diameter is mixed into the blending raw material to make a granulated material. A prescribed quantity of solid fuel (B) adjusted to <=5 mm grain diameter is mixed into this granulated material and granulated to make pseudo-grain coated with the solid fuel (B). This pseudo-grain is sintered with an endless-moving grate type sintering machine to obtain the sintered ore having 20% to <90% pre-reducing ratio. The calorific power of the blast furnace gas is controlled by controlling the pre-reducing ratio of the sintered ore charged in the blast furnace to 20% to <90%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sinter used as a raw material for a blast furnace, a method for producing the same, and a method for operating a blast furnace.

[0002]

2. Description of the Related Art Conventionally, as a raw material for a blast furnace, a sintered ore obtained by mixing fine iron ore, a solvent medium, coke fine and the like, granulating the mixture, and then sintering the mixture is used.

[0003] With respect to such a sintered ore, conventionally, the raw material mixing and the granulation process have been adjusted to improve the air permeability, and to improve the flammability by adhering coke breeze to the surface of the pseudo particle. Various attempts have been made to adjust the structure of the blended raw materials and pseudo particles to increase the fuel efficiency.

[0004] For example, Japanese Patent Publication No. 08-9739 discloses a coagulated agglomerate containing coarse-grained coke as a core in order to use coarse-grained coke that cannot be directly charged into a blast furnace as a blast-furnace fuel. A manufacturing method is disclosed.

[0005] This technique is to mix a raw material ore and a coke breeze into iron ore fines, mix and granulate them to produce raw pellets with coarse-grained coke as a core, and coat the raw pellets with coke breeze. Then, the obtained raw pellets are fired in an endless moving grate type sintering furnace to produce a fired agglomerate. Coarse-grain coke having a particle size of 1 to 3 mm is used as the coarse-grained coke to be included as the core of the raw pellets in the coke breeze generated in the lump coke production process. In the process of firing the raw pellets, the coarse-grained coke of the core remains without burning, and when this agglomerate is charged into the blast furnace, the agglomerate is reduced and melted in the blast furnace, and the coarse-grained coke burns. Therefore, it is possible to reduce the coke basic unit corresponding to the amount. That is, the mixing ratio of coarse-grained coke to the raw material of the agglomerate ore was 10 wt. %, The basic unit of coke in the blast furnace is about 1
0% can be reduced.

Since the properties of the sinter have a direct effect on the operation of the blast furnace, attempts have been made to control the operation of the blast furnace by controlling the properties of the sinter. For example, Japanese Unexamined Patent Application Publication No. 04-210432 discloses that a fine ore has 5 to 20 watts.
t. % Coke breeze and anthracite to form an inner layer,
In addition, fine ore, subprimal family and 2-5 wt. % Of coke breeze and anthracite to form an outer layer, thus forming pseudo-particles having a two-layer structure. The pseudo-particles are mixed and granulated as a part of a sintering material, and then fired by a sintering machine. A method for producing a semi-reduced sintered ore is disclosed. In this case, part of the sintered ore is reduced by direct reduction of the melt generated from the outer layer of the pseudo-particles in the sintering process and the solid carbon in the inner layer of coke breeze or anthracite.

In this publication, as another embodiment, coke breeze and anthracite are preliminarily converted into pseudo particles,
l ₂ O ₃ at 2.0 wt. % Or more and coated with fine ore or auxiliary raw material to form two-layer pseudo-particles. The two-layer pseudo-particles are mixed with other main raw materials, auxiliary raw materials, scale, coke breeze, and anthracite by a primary mixer and a secondary mixer. A method of granulating and charging the sintering machine is also disclosed.

Regardless of the quasi-particle form, an endothermic reaction occurs when the melt produced during the sintering process is directly reduced by the solid carbon in the inner layer of coke breeze and anthracite, and thus, usually occurs. The heat of the lower part of the sintering bed is prevented, and the permeability of the sintering bed is improved, so that the sintering production rate and sinter quality are improved. On the other hand, when used in a blast furnace, the fuel ratio and tapping ratio of the blast furnace are improved.

By the way, in the conventional blast furnace operation, the calorific value (latent heat) of the blast furnace generated gas is mainly correlated with the fuel ratio. In general, the higher the fuel ratio, the higher the calorific value of the blast furnace generated gas. Is lower, the calorific value of the blast furnace generated gas is also lower. However, when the blast furnace generated gas is used as a fuel for a heating furnace or the like in an ironworks, it is desirable that the calorific value of the blast furnace generated gas does not change even if the fuel ratio of the blast furnace changes. Further, it is more preferable that there is a technique capable of controlling the calorific value of the blast furnace generated gas independently of the blast furnace fuel ratio, such as increasing the calorific value of the blast furnace generated gas while maintaining the fuel ratio of the blast furnace constant.

Recently, the elimination of CO ₂ is a social need, and therefore, the steel industry is also required to reduce the fuel ratio of blast furnace operation, that is, to reduce the amount of gas generated from the blast furnace.
However, from the viewpoint of using the blast-furnace generated gas as a fuel in an ironworks, reducing the fuel ratio is not preferable because it leads to a decrease in the calorific value of the blast-furnace generated gas. Therefore, also in this case, a technique for controlling the calorific value of the blast furnace generated gas is required regardless of the fuel ratio of the blast furnace.

As described above, in order to control the calorific value of the gas generated from the blast furnace regardless of the fuel ratio of the blast furnace, it is conceivable to control the properties of the sintered ore. Not yet proposed. That is, the technique disclosed in Japanese Patent Publication No. 08-9739 merely reduces the basic unit of lump coke in a blast furnace, and the technique disclosed in Japanese Patent Application Laid-Open No. It merely reduces the fuel ratio and improves the blast furnace tapping ratio.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a sintered ore capable of controlling a calorific value of a gas generated from a blast furnace without depending on a fuel ratio of the blast furnace. An object of the present invention is to provide a manufacturing method and a blast furnace operating method.

[0013]

In order to control the calorific value of the gas generated from the blast furnace without depending on the fuel ratio of the blast furnace, the present inventors have studied various wrist diagrams based on the overall material heat balance. As a result, it has been found that the calorific value of the gas generated from the blast furnace can be controlled independently of the fuel ratio of the blast furnace by changing the preliminary reduction ratio of the sinter charged in the blast furnace.

[0014] Wrist diagram based on the overall material heat balance
As a result of the investigation, for example, the preliminary return of sinter
20% or more and less than 30% (the state before iron oxide reduction)
Fe ₂O₃Pre-reduced state up to FeO)
If the fuel ratio of the blast furnace is kept constant,
The amount of heat can be varied almost in proportion to the sinter
It is also possible to make a preliminary return of the sinter to be charged to the blast furnace.
If the source rate is 30% or more and less than 90%, the blast furnace generated gas
It is possible to change the fuel ratio while keeping the calorific value constant.
It was presumed possible.

As described above, in order to control the calorific value of the gas generated from the blast furnace without depending on the fuel ratio of the blast furnace, the preliminary reduction rate of the sintered ore can be freely controlled in a wide range from 20% to less than 90%. A simple manufacturing method is required.

However, Japanese Patent Application Laid-Open No.
The method for producing a semi-reduced sinter of the technology disclosed in Japanese Patent Publication No. 32 has the following problems.
% To less than 90% cannot be freely controlled. That is, in the method for producing a semi-reduced sintered ore described in this publication, although the pseudo particles have a two-layer structure and the coke fine and anthracite for reduction are directly disposed in the inner layer, the coke fine for fuel in the outer layer is provided. When blending anthracite, coke breeze and anthracite of the fuel are blended in a state of being mixed with fine ore and subgenaceae, so that the flammability is poor and, as a result, the controllability of the preliminary reduction rate is also poor. In addition, in order to control the preliminary reduction rate in a wide range from 20% to less than 90%, it is necessary to determine the amount of coke breeze and anthracite according to the target reduction rate. Since the relationship between the reduction rate and the achieved reduction rate is not specified, it cannot be said that it has controllability of the preliminary reduction rate.

When the preliminary reduction rate is 20% or more and less than 30%, the iron oxide in the sintered ore is reduced to the state of FeO, but when the content of SiO ₂ in the fine ore is high, the reaction of the formula (1) is performed. Is generated, and low-melting-point, low-reducibility firelite is easily generated, so that the reducibility in the blast furnace deteriorates, and the shaft efficiency (the degree of reaching the FeO-Fe reduction equilibrium) specified by the wrist diagram is reduced. Getting worse. As a result, there arises a problem that although the top gas latent heat increases, the fuel ratio also increases. 2FeO + SiO ₂ (gangue) → 2FeO · SiO ₂ (firelite) ... (1)

Further, in the method for producing a calcined agglomerate described in Japanese Patent Publication No. 08-9739, a raw pellet containing granulated coke as a core is produced, and the raw pellet is coated with coke powder. This is a production method in which the obtained raw pellets are fired in an endless moving great sintering furnace, but unburned coarse-grained coke is left inside the product sintered ore, and the unburned coke is burned in a blast furnace. It is hoped that this will reduce the amount of lump coke in the blast furnace. Therefore, a large amount of coke breeze remains in the product sinter, and the strength of the product sinter decreases, and the crushing /
There is a problem that the conveyor burns due to ignition in the cooling process. Further, even if the product sinter is preliminarily reduced, a method for controlling the pre-reduction rate such as the particle size and amount of the granulated coke and the particle size and amount of the coke flour for coating the raw pellets can be achieved. Preliminary reduction rate is unknown.

From these facts, the present inventors have studied a production method capable of freely controlling the preliminary reduction ratio of the sintered ore in a wide range from 20% to 90%.
In the pseudo-particles having a three-layer structure of the outermost layer, the fine powder coke as a fuel is blended in the outermost layer to increase the combustion efficiency of the fine coke, and the amount ratio to the coarse-grained powder coke blended as a core is appropriately determined. Thus, it has been found that the attained reduction rate is controlled, and thereby, the controllability of the attained reduction rate is significantly improved.

The present invention has been made based on such findings, and the first invention is a sintered ore obtained by firing with an endless moving grate type sintering machine, wherein a reduction rate is reduced in the firing step. Has been pre-reduced to a range of 20% or more and less than 30%.

According to a second aspect of the present invention, there is provided a sintered ore obtained by sintering with an endless moving grate type sintering machine, wherein the sinter is preliminarily reduced in a range of 30% or more and less than 90% in the sintering process. The present invention provides a sintered ore characterized by the following. A more preferable range of the reduction ratio is 70% or less.

The third invention is a method for producing a sintered ore which is fired by an endless moving grate type sintering machine, wherein at least the SiO ₂ content in the compounding raw material is 6 wt. % And a predetermined amount of a solid fuel (A) having a particle diameter adjusted to 1 mm to 10 mm mixed with the blended raw material to form a granulated product.
In the next granulation step, a predetermined amount of the solid fuel (B) whose particle diameter has been adjusted to 5 mm or less is mixed with the granulated product and granulated to obtain pseudo particles coated with the solid fuel (B) 2 A method for producing a sintered ore, comprising the following granulation step:

In a fourth aspect based on the third aspect, the ratio of the sum of the weights of the enclosure fuel (A) and the solid fuel (B) to 1 t of the mixed raw material is 4.5 wt. % To 30.0 wt. % And the weight ratio (A) between the solid fuel (A) and the solid fuel (B)
A method for producing a sintered ore, wherein the value of / (B) is 0.8 or more.

According to a fifth aspect, in the third aspect, the sum of the weights of the solid fuel (A) and the solid fuel (B) with respect to 1 t of the product sintered ore is 50 kg / t or more, and the solid fuel (A) and the solid fuel A method for producing a sintered ore, characterized in that the blending amount of a solid fuel is adjusted so that the value of the weight ratio (A) / (B) of the fuel (B) becomes 0.8 or more.

A sixth invention is a blast furnace operating method in which a sinter obtained by firing in an endless moving great type sintering machine is charged into a blast furnace to operate the blast furnace, and the sintering of the charged ore is performed. The preliminary reduction rate in the process is controlled between 20% and less than 90%,
A method for operating a blast furnace characterized by controlling the calorific value of blast furnace gas.

The existing reduced agglomerate is mainly a raw material for an electric furnace, and its reduction rate is as high as 95% or more. In an electric furnace, only melting is performed and no reduction is performed. The manufacturing process is, for example, Midrex process for shaft furnace type, Hy
l-III process and S for rotary kiln type
L / RN process and the like. However, the production amount of these processes is relatively low as compared with the sintering process and the like, and the strength and the like of the product agglomerate are low, so that they are not suitable for blast furnace raw materials.

The purpose of the present invention is to control the calorific value of the gas generated from the blast furnace in the blast furnace independently of the fuel ratio. In order to change the pre-reduction rate of the raw material charged in the blast furnace, ordinary firing is required. It is necessary to maintain physical and metallurgical properties such as production rate, product strength, particle size, reducibility, etc. comparable to those of condensate or pellets. However, since the final reduction is performed in the blast furnace, the preliminary reduction rate does not need to be 95% or more.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. First, the inventors theoretically obtained from a list diagram based on the overall heat balance of the substance, that is, by changing the pre-reduction rate of the blast furnace charge, the blast furnace was independent of the fuel ratio of the blast furnace. The assumption that the calorific value of the generated gas can be controlled will be described with reference to the drawings. FIG. 1 is a graph showing the gas temperature distribution inside the blast furnace, and FIG. 2 is a graph showing the relationship between the reduction equilibrium of iron oxide, the actual gas composition in the furnace, and the degree of iron oxide oxidation.

In FIG. 1, the gas temperature inside the blast furnace is about 150 to 200 ° C. at the top of the furnace and 2000 to 2400 ° C. at the tuyere. Further, the shaft portion has a so-called heat preservation zone, which is a constant temperature region of approximately 1000 ° C. In this heat preservation zone, iron oxide is present in the gas composition and reduction stage slightly deviating from the FeO-Fe reduction equilibrium.

In FIG. 2, the horizontal axis at the top is the oxidation degree of the gas in the blast furnace (in other words, the oxygen atom ratio O /
C). The degree of oxidation of the gas is such that the gas composition is CO
The value is 1 when only the gas is used, and 2 when the gas moves upward while reducing the iron oxide and finally reaches the total amount of CO ₂ (+ N ₂ ). The result is basically the same as that of the gas except that H ₂ and H ₂ O are contained in the gas, except that a slight change appears in the reduction equilibrium diagram. On the other hand, the vertical axis indicates the oxygen atom ratio to the iron atom (O / Fe). F with the highest degree of oxidation
The degree of oxidation of e ₂ O ₃ is 1.5 and that of Fe ₃ O ₄ is 1.
33 and 1.05 for FeO.

The lower part of FIG. 2 is an equilibrium diagram of the reduction of iron oxide by CO. The horizontal axis represents the degree of oxidation of the gas as described above, and the vertical axis represents the reduction equilibrium temperature. According to FIG.
When the temperature is set to 00 ° C., the F at this temperature is lower than the lower stage in FIG.
The degree of gas oxidation (O / C) at the time of e-FeO reduction equilibrium is determined. Since the degree of oxidation of ore (FeO) is 1.05, the point W in the upper part of FIG. 2 is obtained.

On the other hand, when charged from the furnace top ore oxidation degree 1.5, _(hereinafter referred to as operating line) linearly P _T -P B oxidation degree of oxidation degree and gas ore varies along the. The fuel ratio of the blast furnace is determined by the gradient (C / Fe) of this straight line. When the operation of the blast furnace is ideally performed and the reduction equilibrium has been reached, this straight line is in contact with the point W and the fuel ratio takes the minimum value. shift for operation line without passing through the point W, for example through P ₁ point. Here, the ratio of the length of the straight line P ₀ -W to the length of the straight line P ₀ -P ₁ (P _0-
W) / (P ₀ −P ₁ ) represents the reduction degree of the blast furnace,
This is called shaft efficiency. Usually, the shaft efficiency of a blast furnace is about 0.90 to 0.95.

When the pre-reduced sintered ore of the present invention is used as a blast furnace raw material, the oxidation degree of iron oxide at the time of charging the blast furnace is lower than 1.5, so that _PT becomes _PT instead of _PT in FIG. . Thus, the gas composition (oxidation degree) is also reduced, resulting B gas heating value is increased. However, in this case linearly P _T -P _B
Does not change, so the fuel ratio does not change in principle.

When the preliminary reduction rate exceeds 30%
Shifts to point W 'where the ordinate of point W is lower than 1.05
You. Assuming constant shaft efficiency, the operating line is the shaft
Efficiency (P ₀−P₁/ P₀-W ') is constant_{1 '}point
And as a result, the slope of the operation line becomes smaller.
The fuel ratio drops. However, in this case, the degree of oxidation of the gas
It is estimated that the calorific value of gas generated from the blast furnace does not change because there is no decrease
Is done.

That is, the pre-reduction rate is less than 30% (Fe
In the O reduction stage), the degree of oxidation of the blast furnace generated gas decreases according to the preliminary reduction rate, and as a result, the calorific value of the blast furnace generated gas increases. However, it is not possible to reduce the fuel ratio of the blast furnace, and consequently the amount of carbon dioxide generated. However, when the blast furnace generated gas is used as a fuel for a heating furnace or the like in a steelworks, the calorific value of the blast furnace generated gas is improved, so that the total energy consumption of the steelworks can be reduced. If the preliminary reduction rate is less than 20%, the effect of increasing the calorific value of the gas generated from the blast furnace is small.

On the other hand, when the pre-reduction rate is 30% or more (reduction stage in which FeO and some metallic iron are present), the fuel ratio of the blast furnace can be reduced according to the pre-reduction rate, and as a result, the amount of carbon dioxide generated can be reduced. Becomes In other words, the effect of reducing the energy consumption of the blast furnace, which is the energy intensive section of the integrated steelworks, and thereby suppressing the amount of generated carbon dioxide is expected.
However, in this case, a decrease in the degree of oxidation of the blast furnace generated gas (an increase in the calorific value) cannot be expected. Therefore, in the present invention, the preliminary reduction rate in the sintering process is not less than 20% and less than 30%, or 30%.
% Or more and less than 90%. In the present invention, the pre-reduction rate of the sintered ore is set to less than 90%, because it is difficult to make the pre-reduction rate to 90% or more with a normal sintering machine.
Even if achieved, there is a problem such as reoxidation when stored in the yard. From the viewpoint of making the proportion of the solid fuel appropriate, the preliminary reduction rate is preferably 70% or less.

According to the present invention, by controlling the preliminary reduction ratio between 20% and less than 90% and charging the blast furnace in the sintering process of the sinter, regardless of the fuel ratio of the blast furnace, This makes it possible to control the calorific value of the blast furnace gas.
Specifically, such a sinter uses pseudo-particles having a three-layer structure of a core, an inner layer, and an outermost layer, and coarse coke blended as a nucleus is generated from the inner layer during the sintering process. It is preliminarily reduced by reducing the liquid. In addition, the combustion efficiency of the fine coke is increased by blending fine coke as the fuel in the outermost layer, and the ultimate reduction rate is controlled by appropriately determining the ratio of the coarse coke to be blended as the core,
Furthermore, the controllability of the attained reduction rate is thereby greatly improved.

Hereinafter, a method for producing such a sintered ore will be described. FIG. 3 is a process chart showing a process flow for carrying out the present invention. In FIG. 3, 1 is a normal sintering raw material hopper, 2 is a return hopper, 3 is a solvent hopper, 4
Is a coarse-grained coke hopper. 5 is a primary drum mixer, 6 is a disc pelletizer, 7 is a fine coke hopper, 10 is a shuttle conveyor, 11 is an endless moving grate type firing furnace, and 12 is an ignition furnace.

In the above facilities, a predetermined amount of a sintering raw material, a solvent medium, and coarse-grained coke are cut out from each hopper, supplied to the drum mixer 5, and mixed while adding water. Subsequently, the mixed raw material is supplied to a disc pelletizer 6,
Granulate while adding water. At this time, raw pellets having coarse-grained coke as a core are formed. Next, the raw pellets granulated by the disk pelletizer 6 are supplied to the secondary drum mixer 8 and mixed while adding water and coke breeze cut out from the coke breeze hopper 7. By this mixing, pseudo-particles having a particle size of 2 to 20 mm, the surface of which is coated with coke breeze, are produced. The pseudo-particles coated with coke breeze are charged into a firing furnace 11 via a shuttle conveyor 10, ignited on the surface of a charged material layer by an ignition furnace 12, and fired by sucking air downward. In addition, when granulation is sufficiently performed by the primary drum mixer 5 according to the raw material conditions, the granulation step by the disk pelletizer 6 may be omitted.

FIG. 4 is a cross-sectional view of a pseudo-particle having a three-layer structure obtained in the production process of the present invention. 13 is a coarse-grained coke which forms the nucleus of pseudo-particles, 14 is an inner layer formed from a mixture of fine ore, ore return, and a solvent medium, and 15 is an outermost layer made of fine-grained coke. In general, a mixture of a plurality of brands of fine ore, a source of miscellaneous iron, and an auxiliary material is referred to as a new raw material, and a mixture of the new raw material and returned minerals is referred to as a blended raw material. The auxiliary materials include a solvent such as a solvent and quick lime. Further, a mixture of the blended raw material and the solid fuel is referred to as a mixed raw material.

In the present invention, the content of SiO ₂ in the compounding raw material is set to 6 wt. Adjust to less than%. This is because 6
wt. % Of SiO ₂ , a large amount of firelite is generated by the reaction shown in the above formula (1) during the firing process.
In the lump zone below 100 ° C, it shows poor reducibility, causing reduction stagnation, and in the softening / melting zone above 1000 ° C, a large amount of low melting point slag is generated to worsen the burn-through yield of the softening / melting zone. This is an obstacle to the reduction of the blast furnace fuel ratio.

As the medium solvent, usually quick lime is desirable, but in addition to slaked lime and bentonite, fine powder slag, portland cement and the like may be used.

As the solid fuel, anthracite, coal, char, petroleum coke and the like can be used in addition to the coke batter and the fine coke. Here, coke breeze will be described as an example for convenience.

The coarse-grained coke functions as a nucleus in the mixing / granulating process by the primary mixer, and the coarse ore or the medium solvent adheres around the coarse-grained coke to be granulated. Also,
In the sintering process, reduction is caused from inside the pseudo particles, and reoxidation of the reduced structure is suppressed. Therefore, the coarse powder coke particle size is 1 mm or more and less than 10 mm, preferably 3 to 8 m.
m is effective. If the particle size is 1 mm or less, it does not function as a nucleus in the granulation step, and it is difficult to form a granulated product having coarse powder coke as a nucleus and a sintering raw material adhered to the periphery. Therefore, the reduction from the inside of the pseudo particle as intended by the present invention is also insufficient. On the other hand, if it is 10 mm or more, a large amount of carbon material remains in the sintered product agglomerate after sintering, and ignites in the crushing and cooling steps after the great, causing burnout of the conveyor and a reduction in the strength of the crystalline agglomerate.

[0045] The fine coke for coating is a fuel for supplying the calorie required for firing. In order to increase the combustion efficiency, the fine particle coke is coated on the surface layer of the pseudo particle. At that time, it is important to form a uniform and strong coating layer on the surface layer of the pseudo particle. Further, since the change in the amount of fine coke is directly reflected in the calorific value, the calorie controllability is excellent. The smaller the coke breeze particle size, the better, the upper limit is 5 mm, preferably 1
mm or less.

In order to achieve the target preliminary reduction rate, it is necessary to set the ratio of coke breeze in the mixed raw material to a predetermined value. The correlation between the pre-reduction ratio and the ratio of coke breeze in the mixed raw material differs depending on various conditions at each factory, and may be determined for each factory. For example, when the target value of the preliminary reduction rate is set in a range of 20% or more and less than 30%, the ratio of coke breeze in the mixed raw material is set to 4.5 w.
t. % To 8.5 wt. %, The correlation between the preliminary reduction rate and the ratio of coke breeze in the mixed raw material is determined, and the ratio of coke breeze in the mixed raw material is determined based on the correlation.

The coke breeze ratio in the mixed raw material was 4.5 wt. %, The FeO content in the product sintered ore is 10 to 15 wt. %, Which has little effect on improving the calorific value of the gas generated from the blast furnace. On the other hand, the amount of coke breeze was 8.5 wt. %, The calorific value of the gas generated from the blast furnace is saturated.

Similarly, when the pre-reduction rate is set in the range of 30% or more and less than 90%, the ratio of the solid fuel in the mixed raw material is 8.5 wt. % To 30 wt. The correlation may be obtained by changing the correlation in the range of%. The ratio of coke breeze is 30.0w
t. %, The combustion time of the coke breeze becomes extremely long, so that the production rate of the sintered ore deteriorates, and the amount of heat supplied to the sintering bed increases weekly, resulting in a remarkable increase in the amount of melt produced in the bed. Bed permeability deteriorates.

The amount of coke breeze to be added is, as described above,
It may be expressed by a coke ratio which is a ratio to the mixed raw material, or may be expressed by a unit of coke per ton of sintering production. Using the following relational expression, conversion between the coke ratio and the coke intensity can be performed. Coke basic unit (kg / t) = ｛Coke ratio (%) ×
(Use of new raw materials (kg / t) + return of ore (kg / t)
t))｝ / (new material usage (kg / t) × sintering yield (%)) × 1000

The sintering yield of a general sintering machine is about 91.0.
%, New raw material usage is 1110 kg / t, returned ore usage is 2
Since it is 00 kg / t, the coke ratio of 4.5% is converted to a coke basic unit of 58 kg / t.

Therefore, similarly, the correlation between the preliminary reduction rate and the coke basic unit is obtained by changing the coke basic unit within the above range, and the coke basic unit for the target preliminary reduction rate can be determined.

Also, regardless of the range of the pre-reduction ratio, the ratio of the amount of coarse coke for the interior (nucleus) and the amount of fine coke for the exterior (coating) in the solid fuel (internal / exterior ratio = interior / interior amount / It is preferable to set the amount of exterior to 0.8 or more. If the ratio of the interior and exterior of the solid fuel is 0.8 or less, the reduction ability for reducing from inside the pseudo particle is insufficient. In addition, as the amount of coke breeze mixed as the core decreases, the exterior ratio increases, so that the combustion heat becomes excessive and the production rate decreases as in the case described above.

[0053]

Embodiments of the present invention will be described below. (Example 1) In practicing the present invention, pseudo particles were produced according to the granulation process shown in FIG. 3, and the pseudo particles were fired in a test pan. The controllability of the reduction rate was confirmed. For convenience of explanation, a sintered ore having a preliminary reduction rate of less than 30% (reduction to FeO) is an L-type sintered ore, and a preliminary reduction rate of 30% to 90%.
% Of sintered ore is classified into H-type sintered ore.
In the following, an L-type sintered ore will be described, and in Example 2 described later, an H-type sintered ore will be described.

In this example, Table 1 shows the chemical composition and particle size of the raw materials used for firing the L-type sintered ore in the test pot. SiO ₂ content in the compounding raw material is 4.6
3 wt. %. It should be noted that there are 15 returned minerals
wt. % And 2.5% by weight of quicklime as a binder. %. The solid fuel has a coarse particle coke having a particle size of 3 to 5 mm for the interior (core) and a particle size of 3 to 5 mm for the exterior (coating).
Fine coke adjusted to not more than mm was used.

First, a primary drum mixer (inner diameter 4.4 m, effective length 15 m) was mixed and granulated while adding an appropriate amount of water to the blended raw material and a predetermined amount of coarse-grained coke. Subsequently, the granulated material of the primary drum mixer is supplied to a secondary drum mixer (inner diameter 5.0 m, effective length 18 m), and the remaining water to be added as necessary and a predetermined amount of fine coke are added. And mixed and granulated. From this, the coke addition amount was 4.5 wt. It is clear that no improvement is seen in the preliminary reduction ratio when the ratio is less than 0.8% and that the improvement effect of the preliminary reduction ratio is small even with the same coke powder addition amount when the interior / exterior ratio is less than 0.8.

As shown in Table 2, the pseudo particles were prepared by mixing solid fuel with 4.5 wt. % To 8.5 wt. %, And five kinds of L1 to L5 were produced. The ratio of the interior (core) coarse-grained powder coke and the exterior (coating) fine-grained coke in the solid fuel (inside / outside ratio = interior amount / exterior amount)
It was appropriately changed in the range of 0.8 or more and 1.4 or less.

As a comparative example, a solid fuel was mixed with 4.5 wt. %, And L7, in which the internal / external ratio of the solid fuel was less than 0.8, was also manufactured.

Each of the produced pseudo particles L1 to L7 has a particle diameter at the outlet of the secondary drum mixer of 2 to 20 mm, has a core of coarse-grained coke at the center, and has a three-layer structure in which the outermost coat is coated with fine-grained coke. Were pseudo particles. In addition, since the sintering raw materials having the particle sizes shown in Table 1 have few fine powder raw materials, granulation can be sufficiently performed only by the primary drum mixer. Therefore, the granulating step using a disk pelletizer was omitted.

Next, the pseudo particles L1 to L7 were fired in a test pan, and the preliminary reduction ratio was measured by the JIS method. The measurement results of the preliminary reduction ratio are as shown in Table 2. In addition,
The firing conditions using the test pot were as follows: pot diameter was 300 mmφ, raw material depth was 450 mm, suction negative pressure was 1000 mmAq, and ignition time was 90 seconds.

FIG. 5 is a graph in which the measurement results of the preliminary reduction rates of L1 to L7 are plotted against the amount of solid fuel (the amount of coke added). From FIG. 5, it is found that the amount of coke breeze added is 4.5 wt. % To 8.5 wt. %, The pre-reduction ratio was approximately 20% to 30%, and it was confirmed that the amount of coke breeze and the pre-reduction ratio were in a roughly proportional relationship.
Also, if the interior and exterior ratio of the solid fuel is 0.8 or more, the correlation between the amount of the solid fuel and the preliminary reduction rate is improved, that is,
It was also confirmed that the controllability of the preliminary reduction rate was improved.

[0061]

[Table 1]

[0062]

[Table 2]

Embodiment 2 In this embodiment, an H-type sintered ore will be described. Table 3 shows the chemical composition and particle size of the compounding ingredients used. SiO ₂ content in the compounding raw material is 3.9
3 wt. %. It should be noted that this compounding raw material has
wt. % And 2.5% by weight of quicklime as a binder. %. The solid fuel has a particle size of 5 to 8 mm for interior (core) and a particle size of 1 m for exterior (coating).
m or less fine coke was used.

First, a primary drum mixer (with an inner diameter of 4.4) was added while adding an appropriate amount of water to the blended material and the coarse-grained coke.
m, effective length 15 m). Further, the granulated material of the primary drum mixer is transferred to a disk pelletizer (diameter 7.
(5 m, depth 0.5 m). This is because the compounding raw materials having the particle sizes shown in Table 3 are mainly composed of fine powders, and the granulation is not sufficient with the primary drum mixer alone. Therefore, a granulating step using a disk pelletizer is added.

The granules of the disc pelletizer are supplied to a secondary drum mixer (inner diameter 5.0 m, effective length 18 m),
The remaining water to be added as needed and fine powder coke adjusted to a particle size of 1 mm or less were added, mixed and granulated.

As shown in Table 4, the pseudo particles were prepared by mixing the solid fuel with 8.5 wt. % To 30.0 wt. %, And six kinds of H1 to H6 were produced. The ratio of coarse-grained coke for interior (core) and fine-grained coke for exterior (coating) in solid fuel (internal / exterior ratio = interior volume / exterior volume)
Was appropriately changed in the range of 1.0 to 2.5.

As a comparative example, 30.0 wt. % And H8 with an internal / external ratio of the solid fuel of less than 0.8 were also manufactured. All of the produced pseudo particles were pseudo particles having a three-layer structure, as in the case of the L-type.

Next, the pseudo particles H1 to H8 were fired in a test pot, and the preliminary reduction ratio was measured by the JIS method. Table 4 shows the results.
It was shown to. The firing conditions using the test pan are the same as those for the L-type.

FIG. 6 is a graph plotting the results of the preliminary reduction ratios of the sintered ores H1 to H8 with respect to the amount of solid fuel (the amount of coke added). As shown in FIG. 6, in the H-type sintered ore, the coke breeze addition amount was 8.5 wt. % To 30.0 wt. %, The pre-reduction rate was approximately 30% to 90%, and it was confirmed that the amount of coke breeze and the pre-reduction rate were in a roughly proportional relationship.

Also, in the case of H-type sintered ore, it was confirmed that the controllability of the preliminary reduction rate was improved if the ratio of the solid fuel to the interior and exterior was 0.8 or more.

[0071]

[Table 3]

[0072]

[Table 4]

In the above Examples 1 and 2, since the firing was performed in a test pan, the ratio of the solid fuel was 4.5 wt. % To 8.5 wt. % And 8.5
wt. % To 30.0 wt. However, when the solid fuel consumption rate when fired by an actual sintering machine is determined by the above-described method, it is approximately 56 to 106 kg / t product sintering and 106 to 373 kg / t product sintering, respectively. However, when the ratio of the solid fuel is 30.0 wt. % Is too high in consideration of the actual sinter production process, so that the reduction rate is preferably 70% or less when the reduction rate is in the range of 30% or more and less than 90%.

Although not described, in Examples 1 and 2, other conditions for maintaining the sintered ore as the raw material for the blast furnace were satisfactory.

[0075]

According to the present invention, the calorific value of the gas generated from the blast furnace can be changed while maintaining the fuel ratio of the blast furnace constant by setting the preliminary reduction rate of the sinter to be at least 20% and less than 30%. . Further, by setting the preliminary reduction rate of the sinter to be 30% or more and less than 90%, the fuel ratio can be changed while maintaining the calorific value of the blast furnace generated gas constant. Therefore, the calorific value of the blast furnace generated gas can be controlled without depending on the fuel ratio of the blast furnace. Further, according to the present invention, a method for producing a sintered ore having excellent controllability of the preliminary reduction rate can be obtained. The pre-reduced sintered ore obtained by the production method of the present invention has a reduction rate of 20%.
Even in the range of ３０30%, generation of firelite in the sintering process is suppressed, so that there is no deterioration in sinterability and no reduction in reducibility in a blast furnace. Also, no unburned coke powder remains in the product sinter, which reduces the strength of
There is no problem of conveyor burnout due to ignition in the cooling process.

[Brief description of the drawings]

FIG. 1 is a diagram of a gas temperature distribution in a blast furnace.

FIG. 2 is a diagram showing the relationship between the reduction equilibrium of iron oxide, the degree of oxidation of gas in a blast furnace, and the degree of oxidation of iron oxide.

FIG. 3 is a process chart showing a process flow in the method for producing a sintered ore of the present invention.

FIG. 4 is a cross-sectional view of a pseudo particle having a three-layer structure obtained by the present invention.

FIG. 5 is a graph showing a relationship between a solid fuel ratio (coke addition amount) and a preliminary reduction ratio in Example 1 of the present invention.

FIG. 6 is a graph showing a relationship between a solid fuel ratio (coke addition amount) and a preliminary reduction ratio in Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sintering raw material hopper 2 ... Remineralized hopper 3 ... Medium solvent hopper 4 ... Coarse powder coke hopper 5 ... Primary drum mixer 6 ... Disc pelletizer 7 ... Fine powder coke hopper 10 ... Shuttle conveyor 11 ... Endless moving great firing furnace 12 ... Ignition furnace

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidetoshi Noda 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Koichi Ichikawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Tomoo Kamoshida 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4K001 AA10 BA01 CA16 CA35 CA39 GA02 GA10

Claims (6)

[Claims] 1. A sintered ore obtained by sintering with an endless moving grate type sintering machine, wherein the sinter is preliminarily reduced to a reduction ratio of 20% or more and less than 30% in a sintering process. Sinter. 2. A sintered ore obtained by calcining with an endless moving grate type sintering machine, wherein the ore is preliminarily reduced to a range of 30% or more and less than 90% in a firing process. Sinter. 3. A method for producing a sintered ore which is fired by an endless moving great type sintering machine, wherein at least S
iO ₂ content of 6 wt. %, A primary granulation step of mixing a predetermined amount of the solid fuel (A) having a particle diameter adjusted to 1 mm to 10 mm with the compounded raw material to form a granulated product, A predetermined amount of the solid fuel (B) whose particle diameter has been adjusted to 5 mm or less is mixed and granulated, and the solid fuel (B) is mixed.
And a secondary granulation step of forming pseudo-particles coated with sintering. 4. The ratio of the sum of the weight of the enclosure fuel (A) and the weight of the solid fuel (B) to 1 t of the mixed raw material is 4.5 wt. % -3
0.0 wt. 4. The sintered ore according to claim 3, wherein the value of the weight ratio (A) / (B) of the solid fuel (A) and the solid fuel (B) is 0.8 or more. 5. Manufacturing method. 5. The sum of the weights of the solid fuel (A) and the solid fuel (B) per 1 ton of the product sintered ore is 50 kg / t or more, and the weight ratio of the solid fuel (A) and the solid fuel (B). (A)
The method for producing a sintered ore according to claim 3, wherein the blending amount of the solid fuel is adjusted so that the value of / (B) becomes 0.8 or more. 6. A method for operating a blast furnace by charging a sintered ore obtained by firing with an endless moving grate type sintering machine into a blast furnace, the method comprising: A method for operating a blast furnace, characterized in that the calorific value of the blast furnace gas is controlled by controlling the preliminary reduction rate between 20% and less than 90%.