JP4529838B2 - Sinter ore and blast furnace operation method - Google Patents

Description

  The present invention relates to a sintered ore used as a blast furnace raw material and a blast furnace operating method.

  Conventionally, as a blast furnace raw material, a sintered ore obtained by mixing and granulating powdered iron ore, a solvent medium, powdered coke and the like, and then sintering has been used.

  With regard to such sintered ore, conventionally, adjusting the raw material blending and granulation process to improve air permeability, adhering powder coke to the surface of the pseudo particles to improve combustibility, Various attempts have been made to improve the fuel efficiency by adjusting the structure of the pseudo particles.

  For example, Patent Document 1 discloses a method for producing a calcined agglomerated mineral in which coarse-grained coke is used as a core in order to use coarse-grained coke that cannot be charged directly into the blast furnace as a blast furnace fuel. .

  This technology combines powdered iron ore with a medium and powdered coke, mixes and granulates to produce raw pellets with coarse powdered coke as the core, and coats the raw pellets with powdered coke. A fired agglomerate is produced by firing the green pellets obtained in an endless moving great-type sintering furnace. As the coarse-grained coke that is contained as the core of the raw pellet, small-sized coke having a particle diameter of 1 to 3 mm is used among the powdered coke generated in the lump coke production process. During the firing process of raw pellets, the core coarse coke 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 coke is burned. , It is possible to reduce the lump coke intensity per unit. That is, the blending ratio of the coarse-grained coke to the raw material of the agglomerated mineral is 10 wt. %, The blast furnace lump coke intensity can be reduced by about 10%.

  In addition, since the properties of sintered ore directly affect blast furnace operation, attempts have been made to control blast furnace operation by controlling the properties of sintered ore. For example, in Patent Document 2, 5 to 20 wt. % Of powdered coke and anthracite and granulated to form an inner layer, and powdered ore, auxiliary materials and 2 to 5 wt. % Coke and anthracite are mixed and coated to form an outer layer. In this way, pseudo-particles having a two-layer structure are formed, and the pseudo-particles are mixed and granulated as part of the sintering raw material, and then sintered in a sintering machine. As a result, a method for producing a semi-reduced sintered ore is disclosed. In this case, a part of the sintered ore is reduced by direct reduction of the melt generated from the outer layer of the pseudo particles during the sintering process and the solid carbon in the inner layer of powder coke and anthracite.

Moreover, in patent document 2, as another aspect, powder coke and anthracite are pseudo-particled in advance, and Al ₂ O ₃ is added to the pseudo particles by 2.0 wt. 2% pseudo particles by coating with powdered ore containing 2% or more and auxiliary materials, etc., and mixing these two layer pseudo particles together with other main raw materials, auxiliary raw materials, scale, powder coke, anthracite in primary mixer and secondary mixer. A method of granulating and charging into a sintering machine is also disclosed.

  Regardless of the quasi-particle form, an endothermic reaction occurs when the melt produced in the sintering process is directly reduced by the solid carbon in the inner layer of powdered coke and anthracite. Excessive heat in the lower layer is prevented and the air permeability of the sintered bed is improved, so that the sintering production rate and the quality of the sintered ore are improved. On the other hand, when used in a blast furnace, the fuel ratio and output 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. Generally, the higher the fuel ratio, the higher the calorific value of the blast furnace generated gas, and the lower the fuel ratio. The calorific value of the blast furnace gas is also reduced. However, when the blast furnace generated gas is used as a fuel for a heating furnace or the like in the steelworks, it is desirable that the amount of heat generated by the blast furnace generated gas does not vary even if the fuel ratio of the blast furnace varies. Furthermore, it is more preferable if there is a technique capable of controlling the heat generation amount of the blast furnace generated gas irrespective of the fuel ratio of the blast furnace, such as increasing the heat generation amount of the blast furnace generated gas while keeping the fuel ratio of the blast furnace constant.

Recently, CO ₂ reduction 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 in the blast furnace. However, from the viewpoint of using the blast furnace generated gas as fuel in the ironworks, a reduction in the fuel ratio is not preferable because it leads to a decrease in the amount of heat generated by the blast furnace generated gas. Therefore, in this case as well, a technique for controlling the calorific value of the gas generated in the blast furnace regardless of the fuel ratio of the blast furnace is required.

Thus, in order to control the calorific value of the blast furnace generated gas regardless of the fuel ratio of the blast furnace, it is conceivable to control the properties of the sintered ore. However, a technology that takes this into account has not yet been proposed. Not. In other words, the technique disclosed in Patent Document 1 merely reduces the basic unit of blast furnace coke, and the technique disclosed in Patent Document 2 reduces the fuel ratio of the blast furnace and releases the blast furnace. It is only something that improves the ratio.
Japanese Patent Publication No. 08-9739 Japanese Patent Laid-Open No. 04-210432

  The present invention has been made in view of such circumstances, and an object thereof is to provide a sintered ore and a blast furnace operating method capable of controlling the heat generation amount of blast furnace generated gas without depending on the fuel ratio of the blast furnace. And

  In order to control the calorific value of the gas generated in the blast furnace without depending on the fuel ratio of the blast furnace, the present inventors have studied various list diagrams based on the overall material heat balance, and as a result, It was found that by changing the reduction rate of the ore, the calorific value of the gas generated in the blast furnace can be controlled without depending on the fuel ratio of the blast furnace.

As a result of the examination of the list diagram based on this general mass heat balance, for example, the reduction rate of the sintered ore charged into the blast furnace is 20% or more and less than 30% (the state before reduction of iron oxide is Fe ₂ O ₃ The pre-reduction state up to FeO at the same time), the calorific value of the gas generated in the blast furnace can be changed almost in proportion to the reduction rate of the sintered ore while keeping the fuel ratio of the blast furnace constant. In addition, it was estimated that if the reduction rate of sintered ore charged into the blast furnace is 30% or more and less than 90%, it is possible to change the fuel ratio while maintaining the calorific value of the blast furnace generated gas constant. .

  Thus, in order to control the calorific value of the gas generated in the blast furnace without depending on the fuel ratio of the blast furnace, there is a manufacturing method that can freely control the reduction rate of the sintered ore over a wide range from 20% to less than 90%. is necessary.

  However, the semi-reduced sintered ore production method disclosed in Patent Document 2 has the following problems, and the reduction rate of the sintered ore can be freely controlled over a wide range from 20% to less than 90%. I can't. That is, in the method for producing a semi-reduced sintered ore described in Patent Document 2, although the pseudo particles have a two-layer structure and powder coke and anthracite for reduction are directly arranged in the inner layer, the powder for fuel is disposed in the outer layer. When blending coke and anthracite coal, fuel coke and anthracite coal are blended in a state of being mixed with pulverized ore and auxiliary materials, resulting in poor combustibility and consequently poor control of the reduction rate. In order to control the reduction rate in a wide range of 20% or more and less than 90%, it is necessary to determine the amount of pulverized coke and anthracite according to the target reduction rate. Since the relationship of the achieved reduction rate is not clearly shown, it cannot be said that the reduction rate has controllability.

Further, when the reduction rate is 20% or more and less than 30%, the iron oxide in the sintered ore is reduced to the state of FeO. However, when the SiO ₂ content in the fine ore is high, the reaction of the formula (1) occurs and the iron oxide is low Since the melting point / refractory firelite is easily generated, the reducibility in the blast furnace is deteriorated, and the shaft efficiency (reach to the FeO to Fe reduction equilibrium) defined by the list diagram is deteriorated. As a result, although the furnace top gas latent heat increases, the fuel ratio also increases.
2FeO + SiO ₂ (gangue) → 2FeO · SiO ₂ (firelite) (1)

  Moreover, the manufacturing method of the calcined agglomerate described in the said patent document 1 makes the raw pellet which made coarse coke the core, coat | covers this raw pellet with powder coke, and uses the obtained raw pellet. It is a manufacturing method that burns in an endless moving great-type sintering furnace, leaving unburned coarse-grained coke inside the product sintered ore, and burning the unburned coke in the blast furnace to make a lump in the blast furnace. Expect to reduce the amount of coke. Therefore, since a large amount of coke powder remains in the sintered product ore, there is a problem that the strength of the product sintered ore is reduced, or the conveyor is burnt out by firing in the crushing / cooling process at the later stage of the sintering machine. . In addition, even if the product sinter is pre-reduced as a result, the method of controlling the reduction rate such as the particle size and amount of coarse coke and the particle size and amount of powdered coke for coating raw pellets and the reduction that can be achieved The rate is unknown.

  For these reasons, the present inventors have studied a production method in which the reduction rate of the sintered ore can be freely controlled in a wide range of 20% to 90%, and as a result, from the three-layer structure of the core, the inner layer, and the outermost layer. In the quasi-particles, the fine coke that is the fuel is blended in the outermost layer to increase the combustion efficiency of the fine coke, and the ultimate reduction rate is controlled by appropriately determining the quantity ratio with the coarse-grained coke blended as the core In addition, it has been found that the controllability of the ultimate reduction rate is greatly improved.

The present invention has been made based on such knowledge, and the first invention is a sintered ore obtained by firing with an endless moving grate-type sintering machine, wherein the SiO ₂ content in the blended raw material is 6 wt. Coarse powder coke of 1 mm or more and less than 10 mm that functions as a nucleus in the mixing and granulation process, and fine powder coke that covers the surface of the pseudo particle layer that is a fuel for supplying the amount of heat necessary for firing And the ratio of the powder coke in the mixed raw material is 4.5 wt. % To 8.5 wt. %, And the ratio of the amount of coarse-grained coke in the mixed raw material to the amount of fine powder coke for the exterior (coating) (interior / exterior ratio = interior / outside amount) is preliminarily set to 0.8 to 2.5. The correlation between the reduction rate and the ratio of the powdered coke in the mixed raw material is obtained, and based on the correlation, the preliminary reduction rate up to the FeO reduction stage in the firing process is in the range of 20% to less than 30%. Providing a characteristic sintered ore.

The second invention is a sintered ore obtained by firing with an endless moving great-type sintering machine, wherein the SiO ₂ content in the blended raw material is 6 wt. Coarse powder coke of 1 mm or more and less than 10 mm that functions as a nucleus in the mixing and granulation process, and fine powder coke that covers the surface of the pseudo particle layer that is a fuel for supplying the amount of heat necessary for firing Used, the ratio of the powder coke in the mixed raw material is 8.5 wt. % To 30 wt. %, The ratio of the amount of coarse-grained coke in the mixed raw material and the amount of fine coke for the exterior (coating) (interior / exterior ratio = interior amount / outer amount) is 0.8 to 2.5, The correlation between the preliminary reduction rate and the proportion of the coke breeze in the mixed raw material is obtained, and based on the correlation, the preliminary reduction rate up to the FeO reduction stage in the firing process is in the range of 30% or more and less than 90%. Providing a characteristic sintered ore. A more preferable range of the reduction rate is 70% or less.

The third invention is a blast furnace operating method for performing blast furnace operation by charging the sintered ore of the first invention or the second invention obtained by firing with an endless moving great-type sintering machine into the blast furnace. in the range of the pre-reduction rate less than 20% to 30% to FeO reduction step in the process of baking the sintered ore, improving the heating value of the blast furnace gas, and control for less than 30% or more 90%, blast furnace A blast furnace operating method characterized by controlling the fuel ratio is provided.

When the sintered ore is produced by firing with an endless moving great-type sintering machine, at least the SiO ₂ content in the blended raw material is 6 wt. A primary granulation step in which a predetermined amount of a solid fuel (A) having a particle diameter adjusted to 1 mm to 10 mm is mixed with the blended raw material to obtain a granulated product, and the granulated product Sintered ore comprising a secondary granulation step in which a predetermined amount of solid fuel (B) having a particle diameter adjusted to 5 mm or less is mixed and granulated to form pseudo particles coated with solid fuel (B) The manufacturing method can be adopted.

  In this case, the ratio of the sum of the weights of the solid fuel (A) and the solid fuel (B) to the mixed raw material 1t is 4.5 wt. % To 30.0 wt. %, And the ratio of the weight ratio (A) / (B) between the solid fuel (A) and the solid fuel (B) is preferably 0.8 or more.

  Further, 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 ratio of the weight of the solid fuel (A) to the solid fuel (B) (A) It is preferable to adjust the blending amount of the solid fuel so that the value of / (B) is 0.8 or more.

  The existing reduced agglomerates are mainly raw materials for electric furnaces, and the 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, the Midrex process and the Hyl-III process for the shaft furnace type, and the SL / RN process for the rotary kiln type. However, the production amount of these processes is relatively low as compared with the sintering process and the like, and the strength of the product agglomerate is low, so it is not suitable for a blast furnace raw material.

  The present invention aims to control the calorific value of the blast furnace generated gas of the blast furnace regardless of the fuel ratio, and when trying to change the preliminary reduction rate of the blast furnace charging raw material, It is necessary to maintain physical and metallurgical properties such as the production rate, product strength, particle size, reducibility and the like of pellets. However, since the final reduction is performed in the blast furnace, the preliminary reduction rate need not be 95% or more.

  According to the present invention, the calorific value of the gas generated in the blast furnace can be changed while maintaining the fuel ratio of the blast furnace constant by setting the preliminary reduction rate of the sintered ore to 20% or more and less than 30%. Further, by setting the preliminary reduction rate of the sintered ore to 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 gas generated in the blast furnace can be controlled without depending on the fuel ratio of the blast furnace. Moreover, according to this invention, the manufacturing method of the sintered ore excellent in controllability of a preliminary reduction rate is obtained. The pre-reduced sintered ore obtained by the production method of the present invention suppresses the formation of firelite during the sintering process even when the reduction rate is in the range of 20% to 30%. There is no deterioration of reducibility in Moreover, unburned powder coke does not remain in the product sintered ore, and there is no problem of conveyor burnout due to strength reduction of the product sintered ore and ignition in the crushing / cooling process.

Hereinafter, the present invention will be specifically described.
First, the inventor theoretically obtained from a list diagram based on the material general heat balance, that is, by changing the preliminary reduction rate of the raw material charged in the blast furnace, the blast furnace was independent of the fuel ratio of the blast furnace. The presumption that the calorific value of the generated gas can be controlled will be described based on 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 oxidation degree of iron oxide.

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

In FIG. 2, the upper horizontal axis represents the degree of oxidation of the gas in the blast furnace (in other words, the oxygen atomic ratio O / C with respect to carbon atoms). The degree of oxidation of the gas is 1 when the gas composition is only CO at the bottom of the blast furnace, and is 2 when the gas moves to the upper part while reducing iron oxide and finally becomes CO ₂ (+ N ₂ ). is there. The basic idea is the same as this result except that some change appears in the reduction equilibrium diagram even if H ₂ and H ₂ O are contained in the gas. On the other hand, the vertical axis represents the oxygen atom ratio (O / Fe) to iron atoms. The oxidation degree of Fe ₂ O ₃ having the highest oxidation degree is 1.5, 1.33 for Fe ₃ O _{4 and} 1.05 for FeO.

  The lower part of FIG. 2 is a reduction equilibrium diagram of iron oxide by CO. The horizontal axis represents the degree of gas oxidation as described above, and the vertical axis represents the reduction equilibrium temperature. When the temperature of the heat preservation zone is 1000 ° C. from FIG. 1, the degree of gas oxidation (O / C) at the Fe-FeO reduction equilibrium at this temperature is obtained from the lower stage of FIG. Since the oxidation degree of the ore (FeO) is 1.05, the upper W point in FIG. 2 is obtained.

On the other hand, when an ore having an oxidation degree of 1.5 is charged from the top of the furnace, the oxidation degree of the ore and the oxidation degree of the gas change along a straight line P _T -P _B (hereinafter referred to as an operation line). The fuel ratio of the blast furnace is determined by this linear gradient (C / Fe). When the operation of the blast furnace is ideally performed and the reduction equilibrium is reached, this straight line is in contact with the W point and the fuel ratio takes the minimum value. However, in the actual blast furnace, the reduction of iron oxide is more than the equilibrium. Because of the deviation, the operation line does not pass through the W point, for example, passes through the P ₁ point. Here, the ratio (P ₀ -W) / (P ₀ -P ₁ ) of the lengths of the straight line P ₀ -W and the straight line P ₀ -P ₁ represents the degree of reduction equilibrium reached in the blast furnace, and is referred to as shaft efficiency. It is. Usually, the shaft efficiency of a blast furnace is about 0.90 to 0.95.

When using the pre-reduction sinter of the present invention as a blast furnace, since lower than 1.5 degree of oxidation of iron oxide blast furnace instrumentation Nyutoki becomes P _{T "on} behalf P _T in FIG. Thus As a result, the gas composition (oxidation degree) also decreases, and as a result, the calorific value of gas B increases, but in this case, since the slope of the straight line P _T -P _B does not change, the fuel ratio does not change in principle.

When the preliminary reduction rate exceeds 30%, the ordinate of the W point shifts to a W ′ point lower than 1.05. Assuming that the shaft efficiency is constant, the operation line passes through the point P _{1 ′} where the shaft efficiency (P ₀ −P ₁ / P ₀ −W ′) is constant, and as a result, the gradient of the operation line becomes smaller and the fuel ratio becomes smaller. Will decline. However, in this case, it is presumed that the amount of heat generated by the blast furnace gas does not change because there is no decrease in the degree of gas oxidation.

  That is, when the preliminary reduction rate is less than 30% (up to the FeO reduction stage), the degree of oxidation of the blast furnace generated gas decreases according to the preliminary reduction rate, and as a result, the heat generation amount of the blast furnace generated gas is improved. However, the fuel ratio of the blast furnace cannot be reduced, and as a result, the amount of carbon dioxide generated cannot be reduced. However, when the blast furnace generated gas is used as fuel for a heating furnace or the like in the steel works, the calorific value of the blast furnace generated gas is improved, so that the total energy consumption of the steel works can be reduced. If the preliminary reduction rate is less than 20%, the effect of increasing the amount of heat generated by the blast furnace gas is small.

  On the other hand, when the preliminary reduction rate is 30% or more (reduction stage in which FeO and some metallic iron exist), the fuel ratio of the blast furnace can be reduced according to the preliminary reduction rate, and as a result, the carbon dioxide generation amount can be reduced. In other words, it is expected that the energy consumption of the blast furnace, which is a high energy consumption department of the integrated steelworks, is reduced, and the carbon dioxide generation amount is suppressed. However, in this case, a decrease in the degree of oxidation of the gas generated in the blast furnace (an increase in the calorific value) cannot be expected. Therefore, in the present invention, the preliminary reduction rate in the sintering process is set to 20% or more and less than 30%, or 30% or more and less than 90%. In the present invention, the preliminary reduction rate of the sintered ore is set to less than 90% because it is difficult to increase the preliminary reduction rate to 90% or more with a normal sintering machine, and even if it is achieved, the yard is reduced. This is because there is a problem such as reoxidation when stored in the tank. From the viewpoint of making the ratio of the solid fuel moderate, the pre-reduction rate is preferably 70% or less.

  In this way, the present invention controls the smelting ore in the sintering process of the sinter by controlling the pre-reduction rate between 20% and less than 90%, and charging the blast furnace regardless of the fuel ratio of the blast furnace. The amount of heat generation can be controlled. Specifically, such a sintered ore uses pseudo particles having a three-layer structure of a core, an inner layer, and an outermost layer. Coarse powder coke blended as a core is melted from the inner layer during the sintering process. It is pre-reduced by reducing the liquid. Also, by adding fine coke as fuel to the outermost layer, the combustion efficiency of the powder coke is increased, and the ultimate reduction rate is controlled by appropriately determining the amount ratio with the coarse powder coke blended as the core, As a result, the controllability of the ultimate reduction rate is remarkably increased.

  Hereinafter, a method for producing such a sintered ore will be described. FIG. 3 is a process diagram 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, and 4 is a coarse-grained coke hopper. 5 is a primary drum mixer, 6 is a disk pelletizer, 7 is a fine coke hopper, 10 is a shuttle conveyor, 11 is an endless moving great type firing furnace, and 12 is an ignition furnace.

  In the above equipment, a predetermined amount of a sintering raw material, a medium solvent, and coarse-grained coke are supplied from each hopper to the drum mixer 5 and mixed while adding water. Subsequently, the mixed raw material is supplied to the disk pelletizer 6 and granulated 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 the powder coke cut out from the powder coke hopper 7. By this mixing, pseudo particles having a particle diameter of 2 to 20 mm whose surface is coated with powdered coke are formed. Pseudo particles coated with powder coke are charged into the firing furnace 11 via the shuttle conveyor 10, and the ignition raw material layer is ignited by the ignition furnace 12 and baked by sucking air downward. If 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 by the manufacturing process of the present invention. 13 is a coarse-grained coke that forms nuclei of pseudo-particles, 14 is an inner layer formed from a mixture of fine ore, return mineral, and solvent, and 15 is an outermost layer composed of finely ground coke. In general, a mixture of multiple brands of powdered ore, miscellaneous iron sources, and auxiliary materials is called a new raw material, and a mixture of the new raw material with return ore is called a blended raw material. The auxiliary raw materials include a solvent such as a solvent medium and quicklime. Moreover, what added the solid fuel to the mixing | blending raw material is called mixed raw material.

In the present invention, the SiO ₂ content in the blended raw material is 6 wt. Adjust to% or less. This is 6 wt. If SiO ₂ is contained in an amount of more than 50%, a large amount of firelite is generated by the reaction shown in the above formula (1) during the firing process, but this firelite is difficult to reduce in a lump of 1000 ° C or less in a blast furnace. In the softening / melting zone above 1000 ° C, a large amount of low-melting slag is generated to deteriorate the softening / melting-down property of the melting zone and hinder the reduction of the blast furnace fuel ratio. It is.

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

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

  Coarse powder coke functions as a nucleus in the mixing and granulation process by the primary mixer, and the raw powder ore and solvent solvent adhere around the coarse powder coke and are granulated. Further, in the sintering process, reduction is caused from the inside of the pseudo particles, and reoxidation of the reduced structure is suppressed. Therefore, the coarse-grained coke particle size is 1 mm or more and less than 10 mm, desirably 3 to 8 mm. When 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 with coarse powder coke as a nucleus and a sintered raw material attached around it. 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 carbonaceous material remains in the sintered product agglomerate, crushing after the great, igniting in the cooling process, causing burnout of the conveyor, lowering of the product agglomerate strength, and the like.

  The fine coke for coating is a fuel for supplying the amount of heat necessary for firing. In order to increase the combustion efficiency, the fine particle coke is coated on the surface portion of the pseudo particle. In that case, it is important to form a uniform and strong coating layer on the surface layer of the pseudo particle. In addition, since the change in the amount of fine coke is directly reflected in the calorific value, the heat quantity controllability is excellent. The smaller the powder coke particle size, the better. The upper limit is 5 mm, preferably 1 mm or less.

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

  In addition, the ratio of the powder coke in the mixed raw material is 4.5 wt. %, The FeO content in the product sintered ore is 10 to 15 wt. %, Which is almost ineffective for improving the heat generation amount of gas generated in the blast furnace. On the other hand, the amount of powder coke is 8.5 wt. If it exceeds%, the heat generated by the blast furnace gas will be 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. What is necessary is just to obtain | require a correlation in the range of%. The ratio of the powder coke is 30.0 wt. If the amount exceeds 50%, the combustion time of the coke breeze will become extremely long, so the production rate of sintered ore will deteriorate, and the amount of heat generated in the bed will become excessive, resulting in a significant increase in the amount of melt produced in the bed. The air permeability is worsened.

As described above, the amount of powder coke to be added may be represented by a coke ratio, which is a ratio to the mixed raw material, or may be represented by a coke basic unit per ton of sintered production. Conversion can be made between the coke ratio and the basic unit of coke by using the following relational expression.
Coke unit (kg / t) = {Coke ratio (%) × (New raw material usage (kg / t) + Returning consumption (kg / t))} / (New raw material usage (kg / t) × Sintering yield (%)) x 1000

  Since the sintering yield of a general sintering machine is about 91.0%, the amount of new raw materials used is 1110 kg / t, and the amount of returned ore used is 200 kg / t, the coke ratio of 4.5% is a coke basic unit of 58 kg. Converted to / t.

  Accordingly, similarly, the coke basic unit can be changed within the above range to obtain the correlation between the preliminary reduction rate and the coke basic unit, and the coke basic unit with respect to the target preliminary reduction rate can be determined.

  In addition, regardless of the range of the preliminary reduction rate, the ratio of the amount of coarse coke for interior (core) to the amount of fine coke for exterior (coating) in the solid fuel (interior / exterior ratio = interior / outer amount) Is preferably 0.8 or more. When the solid / interior ratio of the solid fuel is 0.8 or less, the reducing ability to reduce from the inside of the pseudo particles is insufficient. In addition, the amount of powdered coke to be blended as the core is reduced, so that the exterior ratio is increased.

Examples of the present invention will be described below.
Example 1
In carrying out the present invention, pseudo particles are produced according to the granulation process shown in FIG. 3, and the pseudo particles are fired in a test pan. It was confirmed. For convenience of explanation, sintered ore with a pre-reduction rate of less than 30% (reduction to FeO) is L-type sintered ore, and sintered ore with a pre-reduction rate of 30% to less than 90% is H-type sintered ore. In this Example 1, an L-type sintered ore will be described, and in an 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 blended raw materials used when firing the L-type sintered ore in a test pan. The SiO ₂ content in the blended raw material is 4.63 wt. %. This blended raw material contains 15 wt. % And quick lime 2.5 wt. % Is blended. As the solid fuel, coarse powder coke having a particle diameter of 3 to 5 mm for the interior (core) and fine coke adjusted to a particle diameter of 3 mm or less for the exterior (coating) were used.

  First, mixing and granulating with a primary drum mixer (inner diameter 4.4 m, effective length 15 m) while adding an appropriate amount of water to the blended raw material and a predetermined amount of coarse-grained coke. Next, the granulated material of the primary drum mixer is supplied to the 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 amount of coke added is 4.5 wt. It is clear that when the ratio is less than%, no improvement is seen in the preliminary reduction rate, and when the interior / exterior ratio is less than 0.8, the effect of improving the preliminary reduction rate is small even when the same amount of coke coke is added.

  As shown in Table 2, the quasi-particles consist of 4.5 wt. % To 8.5 wt. %, 5 types of L1 to L5 were produced. In addition, the ratio of the coarse powder coke for interior (core) and fine coke for exterior (coating) in solid fuel (internal / external ratio = interior amount / exterior amount) is suitably in the range of 0.8 to 1.4. Changed.

  In addition, as a comparative example, solid fuel was added at 4.5 wt. % L6 and L7 having a solid fuel inner / outer ratio of less than 0.8 were also produced.

  Each of the produced pseudo particles L1 to L7 is a pseudo particle having a three-layer structure in which the particle diameter at the outlet of the secondary drum mixer is 2 to 20 mm, the core of coarse coke is at the center, and the outermost layer is fine coke. It was. In addition, since the sintering raw material of the particle size shown in Table 1 has few fine powder raw materials, it can fully granulate only with a primary drum mixer, Therefore The granulation process by a disk pelletizer was abbreviate | omitted.

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

  FIG. 5 is a graph in which the preliminary reduction rate measurement results of L1 to L7 are plotted against the amount of solid fuel (coke addition amount). From FIG. 5, the powder coke addition amount is 4.5 wt. % To 8.5 wt. %, The preliminary reduction rate was approximately 20% to 30%, and it was confirmed that the amount of added powder coke and the preliminary reduction rate were approximately proportional. It was also confirmed that if the solid / interior 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, the controllability of the preliminary reduction rate is improved.

(Example 2)
In this example, an H-type sintered ore will be described. Table 3 shows the chemical composition and particle size of the blended raw materials used. The SiO ₂ content in the blended raw material is 3.93 wt. %. This blended raw material contains 15 wt. % And quick lime 2.5 wt. % Is blended. As the solid fuel, coarse coke having a particle size of 5 to 8 mm for interior (core) and fine coke adjusted to a particle size of 1 mm or less for exterior (coating) were used.

  First, mixing and granulating with a primary drum mixer (inner diameter 4.4 m, effective length 15 m) while adding an appropriate amount of water to the blended raw material and coarse-grained coke. Further, the granulated product of the primary drum mixer was granulated with a disk pelletizer (diameter 7.5 m, depth 0.5 m). This is because the blended raw materials having the particle sizes shown in Table 3 are fine powder raw materials, and granulation is insufficient with only the primary drum mixer, and therefore, a granulation step by a disk pelletizer is added.

  The granulated product of the disk pelletizer is supplied to a secondary drum mixer (inner diameter: 5.0 m, effective length: 18 m), and the remaining moisture to be added as necessary and fine coke adjusted to a particle size of 1 mm or less are added. And mixed and granulated.

  As shown in Table 4, the quasi-particles consisted of 8.5 wt. % To 30.0 wt. 6 kinds of H1 to H6 were produced with the range of%. In addition, the ratio of the coarse powder coke for interior (core) and fine coke for exterior (coating) in the solid fuel (internal / external ratio = interior quantity / outer quantity) is suitably in the range of 1.0 to 2.5. Changed.

  In addition, as a comparative example, solid fuel was mixed with 30.0 wt. % H7 and H8 having a solid fuel inner / outer ratio of less than 0.8 were also produced. The manufactured pseudo particles were all 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 pan, and the preliminary reduction rate was measured by the JIS method. The results are shown in Table 4. In addition, the baking conditions by a test pan are the same as the case of L type.

  FIG. 6 is a graph in which the preliminary reduction rate measurement results of the sintered ores H1 to H8 are plotted against the amount of solid fuel (coke addition amount). From FIG. 6, the powder coke addition amount is 8.5 wt. % To 30.0 wt. %, The preliminary reduction rate was approximately 30% to 90%, and it was confirmed that the amount of powder coke added and the preliminary reduction rate were approximately proportional.

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

  In Example 1 and Example 2 above, since firing is performed in a test pan, the ratio of the solid fuel is 4.5 wt. % To 8.5 wt. % And 8.5 wt. % To 30.0 wt. However, when the solid fuel intensity in the case of firing with 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, the solid fuel ratio is 30.0 wt. % Is too high in view of the actual sinter production process, so that the reduction rate is preferably 70% or less within the range of 30% or more and less than 90%.

  Moreover, although not described, in Example 1 and Example 2, the conditions that the sintered ore should maintain as other blast furnace raw materials were satisfactory.

The figure of the gas temperature distribution in a blast furnace. The figure which shows the relationship between the reduction | restoration equilibrium of iron oxide, the gas oxidation degree in a blast furnace, and an iron oxide oxidation degree. Process drawing which shows the process flow in the manufacturing method of the sintered ore of this invention. Sectional drawing of the pseudo-particle of the 3 layer structure obtained by this invention. The graph which shows the relationship between the solid fuel ratio (coke addition amount) and the preliminary reduction rate in Example 1 of this invention. The graph which shows the relationship between the solid fuel ratio (coke addition amount) and the preliminary reduction rate in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sintering raw material hopper 2 ... Returning 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 type firing furnace 12 …… Ignition furnace

Claims (3)

A sintered ore obtained by firing with an endless moving great-type sintering machine, wherein the SiO ₂ content in the blended raw material is 6 wt. Coarse powder coke of 1 mm or more and less than 10 mm that functions as a nucleus in the mixing and granulation process, and fine powder coke that covers the surface of the pseudo particle layer that is a fuel for supplying the amount of heat necessary for firing And the ratio of the powder coke in the mixed raw material is 4.5 wt. % To 8.5 wt. %, And the ratio of the amount of coarse-grained coke in the mixed raw material to the amount of fine powder coke for the exterior (coating) (interior / exterior ratio = interior / outside amount) is preliminarily set to 0.8 to 2.5. The correlation between the reduction rate and the ratio of the powder coke in the mixed raw material is obtained, and the preliminary reduction rate up to the FeO reduction stage in the firing process is set in the range of 20% to less than 30% based on the correlation. Sinter ore. A sintered ore obtained by firing with an endless moving great-type sintering machine, wherein the SiO ₂ content in the blended raw material is 6 wt. Coarse powder coke of 1 mm or more and less than 10 mm that functions as a nucleus in the mixing and granulation process, and fine powder coke that covers the surface of the pseudo particle layer that is a fuel for supplying the amount of heat necessary for firing Used, the ratio of the powder coke in the mixed raw material is 8.5 wt. % To 30 wt. %, The ratio of the amount of coarse-grained coke in the mixed raw material and the amount of fine coke for the exterior (coating) (interior / exterior ratio = interior amount / outer amount) is 0.8 to 2.5, The correlation between the preliminary reduction rate and the proportion of the coke breeze in the mixed raw material is obtained, and based on the correlation, the preliminary reduction rate up to the FeO reduction stage in the firing process is in the range of 30% or more and less than 90%. Characteristic sintered ore. A method for operating a blast furnace in which a blast furnace is operated by charging the sintered ore according to claim 1 or 2 obtained by firing with an endless moving great-type sintering machine. In the pre- reduction rate up to the FeO reduction stage in the firing process of 20% or more and less than 30%, the calorific value of the blast furnace gas is improved, and the fuel ratio of the blast furnace is controlled between 30 % and less than 90% Blast furnace operation method characterized by.

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