CN102482730B - Unfired carbon-containing agglomerate for blast furnaces and production method therefor - Google Patents

Abstract

The present invention relates to a non-fired carbon-containing lump ore for blast furnaces and a manufacturing method thereof. The carbon content (TC) of the non-fired carbon-containing lump ore is 18-25% by mass, and the ratio CaO/ _SiO2 of the CaO content (mass %) to the SiO ₂ content (mass %) is 1.0-2.0. This non-fired carbon-containing lump ore manufacturing method has the following steps: forming a molded body step, in which the iron-containing raw material, carbon-containing raw material and binder are mixed and kneaded, and the kneaded product is shaped to form obtaining a shaped body; and then curing the shaped body to obtain a non-fired carbonaceous lump ore, wherein the carbon content (TC) of the above-mentioned non-fired carbonaceous lump ore is 18 to 25% by mass and the gangue component is The ratio of CaO content (mass %) and SiO ₂ content (mass %) of CaO/SiO ₂ is 1.0 to 2.0, and in the forming process of the above-mentioned molded body, one selected from the type of ore and the amount of binder is adjusted. more than one matching condition.

Description

Non-fired carbon-containing lump ore for blast furnace and its manufacturing method

technical field

The present invention relates to a non-fired carbonaceous lump ore for blast furnaces, and in particular to a non-fired carbonaceous lump ore capable of lowering the melting point of slag in the lower part of the blast furnace to reduce the ratio of reducing materials in the blast furnace.

this application claims priority based on Japanese Patent Application No. 2009-191966 for which it applied to Japan on August 21, 2009, and uses the content here.

Background technique

In the past, various types of iron-containing dust and carbon-containing dust recovered from various dust collection devices in ironworks were mixed, and a cement-like water-setting binder was added, kneaded, and molded to produce 8~ The 16mm diameter non-fired lump ore is used as a blast furnace raw material.

As a method for producing non-fired carbon-containing lump ore, there is known a method of granulating ironmaking dust to form pellets, followed by curing the pellets to solidify them. The process of granulating the above-mentioned iron making dust to make granules is to adjust the particle size distribution of the dust to an appropriate range, add quicklime, cement and other binders and 5 to 15% of water, and pass the mixture through a disc granulator etc. to granulate to obtain granules.

In the production of such non-fired carbonaceous lump ore, it is required to increase the carbon content (T.C) of the non-fired carbonaceous lump ore in order to reduce the ratio of reducing materials in blast furnace operation.

For example, Patent Document 1 discloses that an iron oxide-containing raw material and a carbon-based carbon material are mixed, a binder is added, kneaded, molded, and cured, thereby producing a non-fired lump ore containing carbon. The carbon-containing non-fired lump ore has 80 to 120% of the theoretical carbon amount required to reduce iron oxide contained in the iron oxide-containing raw material to form metallic iron. In addition, the binder is selected so that the compressive strength at room temperature becomes 7850kN/ ^m2 or more, and mixing, molding, and curing are performed. Since the iron oxide in the non-fired carbon-containing lump ore causes a reduction reaction due to the carbon contained therein, the reduction rate can be improved.

However, in this production method, the carbon content is limited in order to ensure strength, and the effect of sufficiently reducing the ratio of reduced materials in the blast furnace cannot be obtained. In order to sufficiently obtain the effect of reducing the reducing material ratio, when a large amount of this non-fired carbon-containing lump ore is used in a blast furnace, the amount of heat absorbed by the dehydration reaction of the binder in the blast furnace increases. Therefore, there is a disadvantage that a low-temperature thermal storage zone is formed, and reduction pulverization of sintered ore is promoted.

In addition, since quicklime and CaO-based cement are often used as a binder, the CaO content in the non-fired carbon-containing lump ore increases. Therefore, the viscosity of the melt produced from the non-fired carbon-containing lump ore increases excessively during the reaction. As a result, aggregation and burn-through of the generated metal are inhibited. Therefore, there is a disadvantage that the ventilation and liquid permeability of the furnace lower part of the blast furnace are deteriorated.

For example, if non-fired carbonaceous lumps are melted and dripped at a low temperature, the non-fired carbonaceous lumps melt at an early stage in the shaft furnace and tend to flow into gaps between raw materials filled in the furnace. In this case, the period of contact with coke is prolonged. As a result, the reduction reaction of the powdery iron ore in the non-fired carbon-containing lump ore and the carburization reaction of the generated iron can be promoted.

Patent Document 2 focuses on the fact that the melting temperature can be lowered by coating CaCO ₃ even with surface-enriched powdered iron ore in which SiO ₂ and Al ₂ O ₃ are generated. In addition, based on this point of view, a non-fired carbon-containing lump ore in which powdery iron ore and a flux are bonded through coal has been proposed.

In addition, Patent Document 2 discloses a carbon-containing lump ore containing 23.3 to 24.6% by mass of coal. Generally, the carbon content of coal is about 70%, and the remainder is ash and volatile components. Therefore, the carbon content in the carbon-containing lump ore corresponds to 16 to 17% by mass.

On the other hand, many reports have been made on the relationship between the dripping property of sintered ore and the composition.

For example, Non-Patent Document 1 reports that the dropping temperature of sintered ore changes nonlinearly with respect to CaO/SiO ₂ , and that the dropping temperature decreases the most near the CaO/SiO ₂ ratio of 1.0, and that the dropping temperature decreases when MgO is increased. .

In addition, Non-Patent Document 2 reports that when 2% of MgO is added to dust cold-bonded pellets (cement bonded) containing 7% carbon, the high-temperature ventilation resistance decreases.

As described above, it is known to optimize the CaO/SiO ₂ and MgO in the gangue composition in order to improve the metal dripping properties of sintered ore and dust particles with a carbon content of less than 10%. However, metal dripping properties of carbon-containing agglomerates with a high carbon content (18 to 25% by mass) whose reduction behavior is completely different, and the optimum conditions for the slag melting point in the lower part of the furnace that determine the metal dripping properties have not yet been clarified.

In addition, the inventors investigated the reduction characteristics of carbon-containing lump ore with high carbon content (total C content 20%, total Fe content 40%, CaO 11%, SiO 6%, Al ₂ O ₃ 2.5%, MgO 0.5%) . Fig. 8 shows the temperature for conventional sintered ore (total Fe content 58.5%, FeO 8%, CaO 10%, SiO ₂ 5%, Al ₂ O ₃ 1.7%, MgO 1.0%) and carbon-containing lump ore with a large carbon content. relationship with recovery rate. Referring to FIG. 8 , it can be seen that carbon-containing lump ore is remarkably reduced in a low temperature range compared with conventional sintered ore. This is a major feature of carbonaceous lump ores with a high carbon content.

Next, using the reduction rate shown in FIG. 8 obtained from the results of the above-mentioned reduction test, the change of the slag melting point (CaO—SiO ₂ —Al ₂ O ₃ —MgO—FeO) caused by the reduction was simulated by computer. It should be noted that in the iron components of sintered ore and carbon-containing lump ore, it is assumed that all unreduced iron exists in the form of FeO, and the slag melting point is calculated from the reduction rate. The results are shown in Fig. 9 . Here, the melting point refers to the temperature at which the entire liquid phase is formed, and a molten liquid is formed even below the melting point. However, when the melting point is high, the amount of melt decreases, so the melting point indirectly indicates the amount of melt.

Referring to Fig. 9, it can be considered that the melting point of sintered ore at 1200°C to 1400°C is basically the same as the temperature of the sample, and a large amount of molten liquid is generated in this temperature range. In contrast, the slag melting point of carbonaceous lump ore rises significantly from around 900°C to over 1600°C. Therefore, it is considered that the carbon-containing lump ore with a high carbon content is reduced in a state where the amount of molten liquid is extremely small. Therefore, since a solid phase usually exists, aggregation of the above-mentioned metals is hindered, which causes deterioration of dripping. In the above-mentioned 5-component system (CaO-SiO ₂ -Al ₂ O ₃ -MgO-FeO), for a carbon-containing lump ore with a high carbon content, FeO greatly affects the melting point, and the reduction proceeds rapidly at a low temperature. The results shown in Figure 9 are a phenomenon specific to carbonaceous lump ores with a high carbon content.

As described above, reduction of carbon-containing lump ore with a high carbon content remarkably proceeds in a low-temperature range compared with sintered ore, and reduction is performed with an extremely small amount of molten liquid. Therefore, the knowledge about the dripping characteristics during reduction of sintered ore cannot be directly applied to carbon-containing lump ore having a high carbon content.

When carbon-containing lump ore is used in a blast furnace, when the melting point of slag is high, the lower surface of the reflow zone decreases, the area of the lower dripping zone becomes narrower, and the retention of slag in the dripping zone and the furnace core increases. Specifically, in the drip zone and the furnace core (area where the metal and slag flow to the concave portion while being separated by specific gravity), the flow of the melt is not smooth, and the melt stagnates in the void (flow path). As a result, the flow of the gas is deviated, and uniform gas heating cannot be performed. For this reason, a heat deficiency locally appears, and it becomes difficult to stabilize the ventilation in the lower part of the furnace.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2003-342646

Patent Document 2: Japanese Patent Laid-Open No. 2005-325412

non-patent literature

Non-Patent Document 1: ISIJ International 44(2004), p.2057

Non-Patent Document 2: Iron and Steel (鉄と钢), 70(1984), p.S825

Contents of the invention

The problem to be solved by the invention

In the present invention, the compositional conditions of a carbon-containing lump ore having an optimum slag melting point for use in a blast furnace are specified. Based on the findings, an object of the present invention is to provide a non-fired carbon-containing lump ore capable of reducing the reduction material ratio of a blast furnace by lowering the melting point of slag, and a method for producing the same.

means to solve the problem

The inventors of the present invention have found a non-fired carbon-containing lump ore product, which can reduce the slag in the lower part of the furnace by making the CaO/SiO ₂ of the gangue component of the carbon-containing lump ore within a specific range (1.0 to 2.0) Melting point, so that excellent metal dripping properties can be achieved. It has also been found that in order to make the CaO/SiO ₂ of the gangue component of the non-fired carbon-containing lump ore 1.0 to 2.0, it is preferable to adjust the compounding amount of the high SiO ₂ -containing ore and the MgO-containing auxiliary raw material as described later.

A non-fired carbon-containing lump ore for blast furnaces according to an aspect of the present invention is produced by mixing and kneading an iron-containing raw material, a carbon-containing raw material, and a binder, and shaping the kneaded product, A formed body is thus obtained, and the above-mentioned formed body is subsequently cured, wherein the carbon content (TC) is 18 to 25% by mass, and the ratio of the CaO content (mass %) to the _SiO2 content (mass %) of the gangue component is CaO/SiO ₂ is 1.0 to 2.0.

For the non-fired carbon-containing lump ore for blast furnaces according to one aspect of the present invention, it may be composed of CaO content (mass %), SiO ₂ content (mass %), Al ₂ O ₃ content (mass %), MgO The value of gangue amount ((CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content (TC))) represented by content (mass %) and carbon content (TC) (mass %) is 0.25 or less , and the MgO content is 0.5% by mass or more.

Content of the said binder can be 5-10 mass %.

A method for producing a non-fired carbon-containing lump ore for a blast furnace according to an aspect of the present invention includes a step of forming a molded body, in which an iron-containing raw material, a carbon-containing raw material, and a binder are mixed and mixed. refining, forming the kneaded product to obtain a compact; and then curing the above-mentioned compact to obtain a non-fired carbon-containing agglomerate, wherein the carbon content (TC) of the above-mentioned non-fired carbon-containing agglomerate is 18 to 25% by mass _and the ratio of CaO content (mass %) to SiO ₂ content (mass %) of the gangue component is 1.0 to 2.0. And one or more compounding conditions in the compounding amount of the binder.

For the manufacturing method of the non-fired carbon-containing lump ore for the blast furnace of one aspect of the present invention, the CaO content (mass %) and the _SiO content (mass %) of the above-mentioned non-fired carbon-containing lump ore can be used. , Al ₂ O ₃ content (mass %), MgO content (mass %) and carbon content (TC) (mass %) expressed gangue amount ((CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100- The carbon content (TC))) value is 0.25 or less and the MgO content is 0.5% by mass or more, and the above blending conditions are adjusted in the forming step of the above-mentioned compact.

The compounding quantity of the said binder can be adjusted in the range of 5-10 mass %.

In the formation process of the above-mentioned compact, it is also possible to further mix any one or both of auxiliary raw materials and high _SiO2- containing ores, and the above-mentioned auxiliary raw materials are selected from silica, serpentine, olivine, dolomite, nickel slag (Nickel slag), magnesite, and brucite, wherein the carbon content (TC) of the above-mentioned non-fired carbon-containing lump ore is 18 to 25% by mass and the ratio of CaO content to SiO ₂ content is CaO/SiO ₂ The compounding quantity of the above-mentioned auxiliary raw material and high _SiO2 containing ore is adjusted so that it may become 1.0-2.0.

The effect of the invention

The non-fired carbon-containing lump ore for blast furnaces according to one aspect of the present invention has a carbon content sufficient to increase the reduction rate of main iron-containing raw materials for blast furnaces such as non-fired carbon-containing lump ore and sinter. In addition, in the operation of the blast furnace, the melting point of slag can be suppressed lower than conventionally, and excellent reduction-generated slag characteristics (metal dripping properties) can be realized.

Therefore, when the non-fired carbon-containing lump ore according to one aspect of the present invention is used as a part of the iron-containing raw material for a blast furnace, good air permeability can be realized in the lower part of the furnace during operation of the blast furnace. In addition, the reducing material ratio (coke ratio) can be significantly reduced.

The method for producing a non-fired carbon-containing lump ore for blast furnaces according to one aspect of the present invention uses a non-fired process, and therefore can achieve energy saving and _CO2 reduction compared with a fired process. In addition, dust generated in the iron-making process can be reused as iron-containing raw materials and carbon materials by a relatively cheap and simple method.

Description of drawings

Fig. 1 is a graph showing the relationship between the amount of binder (cement) compounded (and the ratio of CaO/SiO ₂ ) and the cold compressive strength.

Fig. 2 is a graph showing the relationship between CaO/SiO ₂ and the melting point of slag in sintered ore and non-fired carbonaceous lump ore when the MgO content is 1.5%.

Fig. 3 is a graph showing the relationship between the MgO content of sintered ore and non-fired carbon-containing lump ore and the melting point of slag when CaO/SiO ₂ is 1.5.

Fig. 4 is a graph showing the relationship between CaO/SiO ₂ and metal dripping rate of non-fired carbon-containing lump ore and sintered ore.

Fig. 5 is a graph showing the relationship between the MgO content of non-fired carbonaceous lump ore and sintered ore and the metal dripping rate.

Fig. 6 is a graph showing the relationship between the value of gangue amount (CaO+SiO ₂ +MgO+Al ₂ O ₃ )/(100-TC) and the metal dripping rate.

Fig. 7 is a graph showing the relationship between the carbon content (T.C) of non-fired carbon-containing lump ore and the metal dripping rate.

Fig. 8 is a graph showing the relationship between the temperature and the reduction rate of a conventional sintered ore and a non-fired carbon-containing lump ore with a high carbon content.

Fig. 9 is a graph showing the relationship between the temperature of a conventional sintered ore and a non-fired carbon-containing lump ore with a high carbon content, and a calculated value of a slag melting point.

Detailed ways

The non-fired carbon-containing lump ore for blast furnaces in this embodiment is produced by mixing and kneading iron-containing raw materials, carbon-containing raw materials, and binders, and molding the kneaded product to obtain a molded body , and then curing the molded body. The carbon content (TC) is 18 to 25% by mass, and the CaO/SiO ₂ of the gangue component is 1.0 to 2.0. As a result, the optimum slag melting point for use in a blast furnace is obtained.

In the present embodiment, the carbon content (T.C) of the non-calcined carbon-containing lump ore is 18 to 25% by mass, preferably 20 to 23% by mass.

When the carbon content is less than 18%, even if the gangue components are adjusted, the effect of reducing the ratio of reducing materials becomes small. When the carbon content exceeds 25% by mass, the minimum cold compressive strength required for use in a blast furnace cannot be obtained.

The ratio of CaO content (mass %) to SiO ₂ content (mass %) of the gangue component of the non-fired carbon-containing lump ore, CaO/SiO ₂ (also referred to as basicity), is 1.0 to 2.0, preferably 1.4 to 1.7.

By making CaO/SiO ₂ a low value within the range of 1.0 to 2.0, the metal dripping rate can be increased. In the case of CaO/SiO2 _exceeding 2.0, the metal drop rate is less than 50%. When CaO/SiO ₂ is less than 1.0, the effect of improving the metal dripping rate is saturated.

In this embodiment, the value of the amount of gangue is preferably 0.25 or less, more preferably 0.22 to 0.25. However, the amount of gangue is a value calculated by the following formula.

Gangue amount = (CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content (TC))

It should be noted that CaO, SiO ₂ , Al ₂ O ₃ and MgO in the formula respectively represent the CaO content (mass %), SiO ₂ content (mass %), and Al ₂ O ₃ content in non-fired carbon-containing lump ore. (mass %) and MgO content (mass %).

By setting the value of the amount of gangue to 0.25 or less, the amount of slag can be reduced and the dripping property can be further improved.

The MgO content is preferably 0.5% by mass or more, more preferably 0.6 to 2.0% by mass. Thereby, the melting point of the low-FeO slag (slag with a small FeO content) is lowered by MgO, and the metal dripping property can be further improved.

The method for producing a non-fired carbon-containing lump ore for a blast furnace according to the present embodiment includes a step of forming a molded body in which an iron-containing raw material, a carbon-containing raw material, and a binder are mixed and kneaded, forming a kneaded product to obtain a formed body; and then curing the formed body to obtain a non-fired carbonaceous lump ore. In the formation process of the molded body, the carbon content (TC) of the non-fired carbon-containing lump ore is 18 to 25% by mass and the ratio of the CaO content (mass %) to the _SiO2 content (mass %) of the gangue component CaO /SiO ₂ to be 1.0 to 2.0, adjust one or more compounding conditions selected from the type of ore and the compounding amount of the binder.

Examples of the iron-containing raw material used in this embodiment include iron-containing dust such as sintering dust and blast furnace dust generated in the ironmaking process, pellet raw materials having a particle size smaller than that of powdered iron ore for sintering, and powdered iron ore for sintering. Finely powdered iron ore produced by crushing and/or sizing iron ore.

The content of gangue components such as iron and _SiO2 varies greatly depending on the type of ore used. Therefore, by selecting the type of ore used, the CaO/SiO ₂ value can be adjusted. In particular, the CaO/SiO ₂ value is greatly affected by the amount of ore with a large SiO ₂ content.

As the ore kind used in the present embodiment, can enumerate: Indian high-silicon ore (Indohisilisiyasu), Robe River mine (Robe River), Yandicoogina mine (Yandicoogina), Vale Itabira mine ( Rio Doce (Itabira), Marra Mamba, etc.

Examples of the carbon-containing raw material used in the present embodiment include blast furnace primary ash, coke dust, finely powdered coke, anthracite, and the like.

Examples of the binder used in this embodiment include: fine powder mainly composed of commonly used blast furnace granulated slag and an aging binder composed of an alkali stimulant, quicklime, Portland cement, and bentonite. wait. The blending amount (added amount) of the binder can be appropriately determined in consideration of other blending conditions and the like. When the blending amount of the binder is too small, it is difficult to sufficiently maintain the cold rolling strength of the non-fired carbon-containing lump ore. In addition, when the compounding amount of the binder is too large, the amount of slag of the non-fired carbon-containing lump ore increases, and the air permeability in the lower part of the furnace becomes unstable. Thus, a stable reduction effect of the reducing material ratio cannot be obtained.

Then, the cold strength of the non-fired carbon-containing lump ore obtained by adjusting the amount of the binder to change CaO/SiO ₂ was examined. The obtained results are shown in Table 1 and Fig. 1 .

Table 1

When the amount of binder (cement) is reduced (CaO/SiO ₂ is reduced), the cold strength is reduced. Then, when CaO/SiO ₂ is less than 1.0 (binder (cement) content is less than 5% by mass), it is difficult to maintain the cold compressive strength of 100 kg/cm ² . When the cold compressive strength of the non-fired carbon-containing agglomerate is less than 100 kg/cm ² , pulverization of the non-fired carbon-containing agglomerate may occur during transportation and loading into a blast furnace. In order to maintain the cold compressive strength at 100 kg/cm ² or more, it is preferable to make the amount of the binder (cement) 5% by mass or more. In addition, when the blending amount of the binder (cement) exceeds 10% by mass, the amount of gangue may increase in some cases. Therefore, it is preferable to make the compounding quantity of a binder (cement) into 10 mass % or less. Therefore, it is preferable that the compounding quantity of a binder is 5-10 mass %.

It should be noted that, in the manufacturing process of mixing, kneading, forming and curing, during curing, free water enters the hydrate in the carbon-containing lump ore through the hydration reaction of cement. Therefore, the total blending amount of the raw materials changes somewhat during the production process, but the amount of change is small and basically no change occurs. Therefore, for example, the compounding quantity of a binder is substantially the same as the binder content in the produced non-fired carbonaceous lump ore. The same applies to other components, and the compounding amount in the manufacturing process is basically the same as the content in the non-fired carbonaceous lump ore.

Therefore, in the non-fired carbon-containing lump ore of the present embodiment, the content of the binder is preferably 5 to 10% by mass, whereby a cold compressive strength of 100 kg/cm ² or more can be realized as described above.

In the present embodiment, it is preferable to further mix auxiliary raw materials and high SiO ₂ -containing ore. Thereby, component adjustment can be performed more strictly. In particular the CaO/ _SiO2 value can be adjusted independently of the amount of binder.

Examples of auxiliary raw materials include silica mainly composed of SiO ₂ , serpentine mainly composed of MgO, olivine, dolomite, nickel slag (nickel slag), magnesite, brucite, and the like. In addition, the high SiO ₂ -containing ore is an ore having a SiO ₂ content of 3.5% by mass or more.

Generally speaking, when the chemical composition of the target non-fired carbon-containing lump ore is specified, the compounding amount of these auxiliary materials and high SiO ₂ -containing ore is automatically determined. Therefore, the compounding quantity of these auxiliary raw materials and a high _SiO2 containing ore is not specifically limited, It determines suitably according to the chemical composition of a non-fired carbon-containing lump ore.

Next, a method of adjusting the CaO/SiO ₂ , MgO content, and gangue amount will be described in more detail.

CaO/SiO ₂ is determined by the amount of CaO and the amount of SiO ₂ contained in the raw materials to be mixed.

CaO is mainly contained in binders, blast furnace primary ash used as a carbon-containing raw material, sinter-type dust and converter-type dust used as an iron-containing raw material, and the CaO content can be adjusted by appropriately adjusting the amount of these. However, when using a cement-based binder with a high CaO content as the binder, the amount of the binder itself needs to be reduced since the CaO content is adjusted so that CaO/SiO ₂ becomes 1.0 to 2.0. Therefore, it is necessary to consider whether sufficient cold compressive strength is obtained.

SiO ₂ and MgO are mainly contained in binders, blast furnace primary ash used as carbon-containing raw materials, sintering dust used as iron-containing raw materials, ash in carbon loss, and the like.

In the present embodiment, if CaO/SiO ₂ in the non-calcined carbon-containing lump ore is 1.0 to 2.0, a constant effect can be brought about regardless of the form of SiO ₂ added (the form of the raw material containing SiO ₂ ). In addition, regarding MgO, if the MgO content is 0.5% by mass or more, a constant effect can be brought about regardless of the form of MgO added (the form of the raw material containing MgO).

When actively reducing the value of CaO/SiO ₂ or making the MgO content 0.5% by mass or more, it is preferable to mix silica, serpentine, olivine, dolomite, nickel slag (nickel slag), magnesite, Auxiliary raw materials such as brucite or ores with high _SiO2 content. Thus, as described above, the CaO/ _SiO2 value and the MgO content can be adjusted independently of the amount of binder. However, when a large amount of these auxiliary materials and high SiO ₂ -containing ore are blended, the amount of gangue increases. Therefore, it is preferable to adjust CaO/SiO ₂ and MgO so that the amount of gangue becomes 0.25 or less.

In the present embodiment, as described above, the numerical ranges of the carbon content (TC), CaO/SiO ₂ , gangue amount, and MgO content are specified. Experimental results showing the critical significance of these numerical ranges are shown below.

The reduction rate at 1400°C was measured for sintered ore with CaO/ _SiO2 of 1.5 and MgO content of 1.5% and non-fired carbonaceous lump ore. In addition, assuming that all unreduced iron exists in the slag as FeO, the FeO concentration in the slag was calculated from the obtained reduction rate. As a result, it was found that the FeO concentration in the slag was 34% when sintered ore was used, and 2% when non-fired carbon-containing lump ore was used. Using this FeO concentration, the relationship between the value of CaO/SiO ₂ or the MgO content and the melting point of slag was examined for sintered ore and non-fired carbonaceous lump ore. In addition, the slag melting point (CaO—SiO ₂ —Al ₂ O ₃ —MgO—FeO) was obtained by simulation performed by a computer.

Figure 2 shows the relationship between CaO/SiO ₂ and the melting point of slag when the MgO content is 1.5%. Figure 3 shows the relationship between the MgO content and the melting point of slag when CaO/SiO ₂ is 1.5.

As shown in Figure 2, it can be seen that for sintered ore and non-fired carbon-containing lump ore, CaO/SiO ₂ has different degrees of influence on the melting point of slag. This is due to the difference in reduction rate (ie, FeO concentration in slag) at high temperature. Specifically, for sinter, when CaO/SiO ₂ is reduced by 1.0, the melting point of slag is reduced by 278°C. In contrast, for non-fired carbon-containing lump ore, when CaO/SiO ₂ decreases by 1.0, the melting point of slag decreases by 620°C. Therefore, the influence of CaO/SiO ₂ in non-fired carbonaceous lump ore is more than 2 times greater than that of CaO/SiO ₂ in sintered ore.

The reduction rate of non-fired carbonaceous lump ore is high at low temperature. When using a non-fired carbon-containing lump ore with a large carbon content compared with a fired lump ore with a low carbon content, it is reduced earlier in the upper part of the blast furnace. Thus, the amount of unreduced iron components (the amount of FeO) remaining in the slag reduced in the upper portion and moved to the lower portion decreases. When the amount of FeO in the slag decreases, the melting point of the slag rises. As mentioned above, the melting point of slag is affected by the basicity (CaO/SiO ₂ ). Therefore, it is considered that the melting point of the slag largely changes depending on the basicity in the non-fired carbon-containing lump ore. In addition, it is considered that the melting point of slag becomes very high when the basicity in the non-fired carbonaceous lump ore is high.

In addition, referring to Fig. 3, it can be seen that for sintered ore, if the MgO content increases by 1.0%, the melting point of slag decreases by 50°C. In contrast, for non-fired carbon-containing lump ore, if the MgO content increases by 1.0%, the melting point of slag decreases by 22°C. Therefore, the influence of the MgO content in the non-fired carbonaceous lump ore is about half of the influence of the MgO content in the sintered ore.

However, strictly speaking, the dripping behavior cannot be determined only by the melting point of slag, but is also affected by the amount of slag and other slag properties (viscosity and wettability with metal, etc.). Therefore, dripping behavior is a complex phenomenon that is not yet fully understood. However, it is known that the compositional conditions for lowering the melting point of slag to promote metal dripping are different between sintered ore and non-fired carbonaceous lump ore.

Then, using a load softening test device, the dripping characteristics of non-fired carbon-containing lumps having various gangue components were examined.

The iron-containing raw material and the carbon-containing raw material are pulverized, mixed with a binder and auxiliary raw materials, and kneaded to obtain a kneaded product. Next, the kneaded product is molded, and the molded body is cured for a predetermined period to manufacture non-fired carbonaceous lump ore. The carbon content TC (total carbon) of the non-fired carbon-containing lump ore was 20% by mass. In addition, the compounding ratio of the iron-containing raw material and the auxiliary raw material is adjusted so that the contents of CaO/SiO ₂ and MgO become predetermined values. The compounding quantity of a binder (cement) was 10 mass %.

Specifically, the gangue amount ((CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content (TC))) was kept constant at 0.22, and the MgO content was kept constant at 0.9% by mass. , CaO/SiO ₂ so that the predetermined value is within the range of 0.5 to 2.5, and the compounding amount of Portland cement and fine powdered silica is adjusted. Thereby, CaO/SiO ₂ of the gangue component is in the range of 0.5 to 2.5 and different non-fired carbon-containing agglomerates are manufactured.

In addition, non-fired carbonaceous lumps with various MgO contents were manufactured with CaO/SiO ₂ kept constant at 2.0.

First, a softening test under load was performed on non-fired carbon-containing agglomerates whose gangue component CaO/SiO ₂ was in the range of 0.5 to 2.5 and each was different.

Assuming actual use of a blast furnace, non-fired carbon-containing lump ore was mixed in a ratio of 10% to normal sintered ore (CaO/SiO ₂ =1.8). At the stage of heating to 1600° C. for reduction, the amount (rate) of metal dripped from the crucible was measured. In addition, the metal drip rate (%) defined by the following formula was calculated.

Metal dripping rate (%) = dripping metal amount / (total Fe amount loaded × 0.95) × 100

In addition, the metal dripping rate was measured similarly about the case of only sintered ore. It should be noted that when the metal dripping rate of the sintered ore is lower than 50%, the lower surface of the reflow zone decreases, and the lower dripping zone area becomes narrower. Therefore, lower air permeability deteriorates, making stable operation difficult.

The obtained results are shown in Table 2 and Fig. 4 .

Table 2

As can be seen from Figure 4, the higher the CaO/SiO ₂ of non-fired carbon-containing lump ore, the lower the metal dripping rate. In particular, when CaO/SiO ₂ of non-fired carbon-containing lump ore exceeds 2.0, it is difficult to maintain a metal dripping rate of 50%. By using non-fired carbon-containing lump ore, indirect reduction is performed from a low-temperature region, so the FeO content in the slag coexisting with the metal in the thermal adhesive layer decreases, and the melting point of the slag rises. Generally, when the molten iron produced by reduction descends to the lower part of the blast furnace, carbon of coke is included, and the carbon content increases (reduction produces metal carburization). The increase in the melting point of the slag prevents the coagulation of the molten iron after the reduction and carburization of the metal, resulting in the results shown in FIG. 4 . When CaO/SiO ₂ is lower than 1.0, although the melting point of coexisting slag is sufficiently low, the slag dropping rate is lower than 50%. This is because, as the proportion of SiO ₂ as a network former increases, the viscosity of the coexisting slag increases, which hinders the aggregation of metals.

In addition, FIG. 4 also shows the measurement results showing the relationship between CaO/SiO ₂ and the metal dripping rate of the sintered ore having an MgO content of 1.5%. A tendency to decrease the metal dripping rate with an increase in CaO/SiO ₂ was also observed for sinter. However, its changes are slow. It can also be confirmed from the results in FIG. 4 that the compositional conditions required to achieve excellent metal dripping properties are different between the non-fired carbon-containing lump ore and the sintered ore.

As described above, in order to increase the metal dripping rate, it is necessary to set CaO/SiO ₂ to 1.0 to 2.0. CaO/SiO ₂ is preferably 1.4 to 1.7, and a metal drip rate exceeding 60% can be realized.

In addition, the load softening test was implemented by the same method about the non-fired carbon-containing lump ore which CaO/ _SiO2 was 2.0 and which had various MgO contents. In addition, the relationship between the MgO content in the non-fired carbon-containing lump ore and the metal dripping rate when the non-fired carbon-containing lump ore was mixed into the sintered ore at a ratio of 10% was examined. The obtained results are shown in Table 3 and Fig. 5 .

table 3

As can be seen from FIG. 5 , it is also effective to increase the MgO content in the non-fired carbon-containing lump ore in order to increase the metal dripping rate. From the change in the metal dripping rate when the non-fired carbon-containing lump ore with a CaO/SiO ₂ ratio of 2.0 is mixed into the sintered ore at a ratio of 10%, it can be seen that the metal dripping rate can be maintained when the MgO content reaches 0.5% by mass or more. 50%. The higher the MgO content, the higher the metal dripping rate. However, the MgO content starts to saturate around 2.0%. This is because the melting point of the above-mentioned low-FeO slag (slag with a small FeO content) is lowered by MgO, so the effect of MgO can be effectively obtained under the condition of higher CaO/SiO ₂ .

Therefore, the MgO content is preferably 0.5% by mass or more. The upper limit is not particularly set.

In addition, FIG. 5 also shows the measurement results showing the relationship between the MgO content rate and the metal dripping rate (%) of the sintered ore whose CaO/SiO ₂ is 2.0. Also in sintered ore, a tendency for the metal dripping rate to increase with an increase in the MgO content was observed. However, this change (influence) is larger than that of non-fired carbon-containing lump ore. It can also be confirmed from the results in FIG. 5 that the compositional conditions required to achieve excellent metal dripping properties are different between the non-fired carbon-containing lump ore and the sintered ore.

In addition, the amount of coexisting slag (the amount of gangue + the amount of unreduced FeO) is also an important factor determining the dripping property. Then, CaO/SiO ₂ was 1.5, MgO was 1.0%, and non-fired carbon-containing lumps with different amounts of gangue were manufactured. The metal dripping rate was measured, and the dripping characteristics were investigated.

As described above, the amount of gangue is calculated by the following formula.

Gangue amount = (CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content (TC))

The obtained results are shown in Table 4 and Fig. 6 .

Table 4

As described above, the FeO concentration in the slag has already decreased to 2% at a relatively low temperature portion, so the influence of the FeO concentration is small. As a result, when the amount of gangue was 0.25 or less, good metal dripping properties were exhibited regardless of the amount of slag. It is considered that when the amount of gangue is in the range of 0.25 or less, the physical properties of slag, such as solid phase ratio, viscosity, and wettability with metal, become the dominant factor of metal dripping property compared with the amount of slag. However, when the amount of gangue exceeds 0.25, the influence of the amount of slag cannot be ignored, and the dripping property deteriorates. Furthermore, if the amount of gangue at this level (more than 0.25) is used, when a large amount of non-fired carbon-containing lump ore is used in the blast furnace, the amount of slag in the hearth will increase significantly, and the slagging operation will be unstable, causing ventilation fluctuations. reason.

From the above results, it can be seen that it is preferable to adjust the composition of the non-fired carbon-containing lump ore so that the amount of gangue ((CaO+SiO ₂ +MgO+Al ₂ O ₃ )/(100-TC)) is 0.25 or less.

Furthermore, the effect of the carbon content (T.C) in the non-fired carbon-containing lump ore on the metal dripping rate was examined.

With MgO at 1.0% by mass and kept constant, gangue amount at 0.22 and kept constant, CaO/ _SiO2 at 0.5, 1.0, 1.5, 2.0 or 2.5, carbon content (TC) at 10, 15, 18, 25 or 30 mass % way, adjust the mixing ratio of raw materials, so as to produce non-fired carbon-containing lump ore.

The metal dripping amount (rate) was measured in the same manner as the above method. The obtained results are shown in FIG. 7 .

table 5

From the results in Fig. 7, it can be known that the metal dripping rate decreases with the increase of carbon content (T.C). This is because, as described above, as the carbon content (T.C) increases, the concentration of FeO in the slag coexisting with the metal decreases.

As described above, in order to achieve stable operation in the blast furnace, the metal dripping rate needs to be 50% or more. It can be seen that when CaO/SiO ₂ is 1.0 to 2.0 and the carbon content (TC) is 25% by mass or less, a metal dripping rate of 50% or more can be achieved. Therefore, the upper limit of the carbon content (TC) needs to be 25% by mass.

It should be noted that, in this embodiment, the ingredients of the non-fired carbon-containing lump ore and the compounding amount of the gangue are adjusted within a predetermined range, but the forming method, shape, and physical structure of the non-fired carbon-containing lump ore ( porosity/void ratio, etc.) is not limited. In the case of a non-fired carbon-containing lump ore for a blast furnace, various forms such as pellets or agglomerates can be used. In addition, various molding methods such as extrusion molding can also be used, and the same effect can be obtained.

In the blast furnace, the charge moves from the upper part to the lower part, and the reducing gas moves from the lower part to the upper part, thereby performing heat exchange and reaction. Therefore, blast furnaces are convective reactors. Usually, in the continuous operation of the blast furnace, the reducing power of the reducing gas may be lost in the upper layer of the ore layer, and the reduction may not proceed sufficiently. In particular, agglomerated ore does not contain carbon and has no self-reducing ability. Therefore, in the case of using the burnt lump ore, the burnt lump ore is not sufficiently reduced in the upper part of the ore layer. Then, when the burnt lump ore moves to the lower part of the blast furnace in an incompletely reduced state, it is reduced in the dripping zone and the furnace core of the blast furnace, causing direct reduction. In such a case, there is a problem that the load on the blast furnace increases and the air permeability deteriorates.

On the other hand, when using the non-fired carbon-containing lump ore of this embodiment, the non-fired carbon-containing lump ore of this embodiment coexists with iron ore in the blast furnace, thereby making it possible to make the upper layer of the ore layer especially The reduction efficiency in the

However, in the non-fired carbon-containing lump ore with a high carbon content, the basicity (CaO/SiO ₂ ) in particular has a large influence on the slag melting point as described above ( FIG. 2 ). In the present embodiment, based on the research results of the above-mentioned inventors, by specifying the carbon content (TC) and CaO/SiO ₂ , favorable metal dripping properties are realized. Therefore, the amount of slag remaining in the drip zone and the furnace core is reduced, and good air permeability can be ensured.

Furthermore, as described above, the non-fired carbonaceous lump ore of the present embodiment coexists with iron ore in the blast furnace, whereby the reduction efficiency can be significantly improved especially in the upper layer of the ore layer. Since the reduction efficiency in the upper layer of the difficult-to-reduce ore layer can be greatly improved, the reduction efficiency in the entire blast furnace can be greatly improved. Therefore, it is possible to reduce reducing materials in an amount greater than the amount of coke equivalent to the remainder of the amount of carbon in the non-fired carbonaceous lump ore of the present embodiment.

Example

As iron-containing raw materials, finely powdered iron-containing raw materials (sintering dust and iron ore) were prepared, and as carbon-containing raw materials, carbon materials (coke dust, fine coke, and blast furnace primary ashes) were prepared. In addition, cement (early-strength Portland cement) was prepared as a binder. It should be noted that, in several examples, secondary raw materials with high SiO ₂ content are also used.

The mixing ratio of the raw materials was adjusted so that the mixing ratio of cement (early-strength Portland cement) was 4 to 9% by mass, and the mixing ratio of the carbon material and the finely powdered iron-containing raw material became various values. These raw materials are mixed together with water, and kneaded with an Iris mixer. The obtained kneaded product was granulated (molded) with a disc granulator to obtain untreated pellets. Next, the untreated pellets were cured in the sun for 2 weeks to produce non-fired carbonaceous lump ore. In addition, the water content of the untreated pellets was adjusted to 10 to 14% by mass depending on the amount of cement to be blended.

The cold compressive strength was measured by the following method based on JISM8718 about the obtained non-fired carbonaceous lump ore. A compressive load is applied to one sample at a predetermined pressurization rate, and the load value at which the sample breaks is measured. Calculate the load value (kg/cm ² ) per unit cross-sectional area. Then, the average value of 100 samples was calculated and used as the strength index.

By the method described above, the slag melting point and metal dripping rate of the non-fired carbon-containing lump ore were measured.

In addition, in a blast furnace having an effective volume of 5500 m ³ , the operation of the blast furnace was performed using non-fired carbonaceous lump ore in an amount of 50 kg/tp as a part of raw materials. Furthermore, the upper K value, the lower K value, wind pressure variation, and reducing material ratio during the operation of the blast furnace were measured, and the average value of the operation results for about one month was obtained. The results are shown in Table 6.

Referring to Table 6, in Example 1, the components were optimized such that CaO/SiO ₂ was 2.0, MgO was 0.6%, and the amount of gangue was 0.22. When used in a blast furnace, the ventilation in the lower part of the furnace is improved, and the ratio of reducing materials is reduced to 470kg/tp. Therefore, the effect of using a non-fired carbon-containing lump ore with a high carbon content is exerted.

In addition, in Example 2, an auxiliary raw material having a high SiO ₂ content was added to increase the SiO ₂ content, and CaO/SiO ₂ was further reduced to 1.0. In this Example 2, since the contents of CaO/SiO ₂ and MgO were within appropriate ranges, the melting point of the slag was lowered. However, since the amount of gangue was increased to 0.28, the metal dripping property was slightly lowered, and the reducing material ratio did not fall too much.

In Example 3, the amount of binder was reduced to 4% in order to reduce the amount of gangue. However, due to the appropriate content of chemical components, the metal dripping rate is improved. However, since the amount of the binder was small, the cold compressive strength was insufficient at 85 kg/cm ² . Therefore, when used in a blast furnace, the amount of powder in the furnace increases, thereby deteriorating upper air permeability, and the reduced material ratio becomes slightly high.

In Example 4, the content of the chemical components was adjusted by blending auxiliary raw materials without reducing the amount of the binder. As a result, it is possible to produce a non-fired carbon-containing lump ore having good metal dripping properties without impairing the cold compressive strength. When used in a blast furnace, the ratio of reducing materials decreases the most.

In Example 5, the CaO/SiO ₂ and the amount of gangue are within the range specified in this embodiment (CaO/SiO ₂ : 1.0 to 2.0, the amount of gangue: 0.25 or less), but the MgO content is set as low as 0.4%. Therefore, the metal dripping rate remained at 52%, and although the reducing material ratio decreased, the effect of reducing the reducing material ratio was relatively small.

In contrast, in Comparative Example 1, a non-fired carbon-containing lump ore with a carbon content (TC) as low as 17% by mass, a CaO/SiO ₂ as low as 1.9, and a MgO content as high as 1.0% was produced. When the carbon content (TC) is low, the melting point of the slag is low enough that there is no problem with the dripping property. However, when used in a blast furnace, since the carbon content is low, it is difficult to reduce the reducing material ratio.

In Comparative Example 2, a non-calcined carbon-containing lump ore was manufactured in which the carbon content (TC) was increased to 20%, and CaO/SiO ₂ was increased to 2.2. The melting point of the slag rises significantly due to the increased reduction rate at low temperatures. Furthermore, since CaO/SiO ₂ exceeds 2.0, metal dripping property falls. However, when used in a blast furnace, the air permeability in the lower part of the furnace deteriorates, and the fluctuation of wind pressure increases remarkably. Due to this, the operation becomes unstable. Therefore, the effect brought by the high carbon content cannot be fully enjoyed, and the reduction material ratio stays at the level of 500kg/tp.

In Comparative Example 3, a high-carbon non-fired carbon-containing agglomerate with a carbon content of 30% and exceeding 25% by mass of the upper limit of the range specified in the present embodiment was produced. Since the content of other ingredients is in an appropriate range, the dripping rate is increased to 65%. However, the cold strength is as low as 60kg/cm ² , and the minimum strength required for use in a blast furnace cannot be obtained. Therefore, the charge amount of powder into the blast furnace increases, and long-term stable operation becomes difficult.

As described above, it can be seen that the metal dripping property is good when the carbon content (TC) is 18 to 25% by mass and the CaO/ _SiO2 is in the range of 1.0 to 2.0 in the non-calcined carbon-containing lump ore. It is possible to reduce the ratio of reducing materials when used in a blast furnace. This effect is particularly remarkable when the value of gangue amount (CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content (TC)) is 0.25 or less and the MgO content is 0.5% by mass or more. . In addition, the cold compressive strength can also be maintained by adjusting the composition by adding the auxiliary raw materials so that the amount of the binder is 5 to 10%.

Possibility of industrial use

The non-fired carbonaceous lump ore for a blast furnace according to one aspect of the present invention has a carbon content sufficient to increase the reduction rate of main iron-containing raw materials for a blast furnace, such as the non-fired carbonaceous lump ore and sinter, when used in a blast furnace. Furthermore, in the operation of the blast furnace, the melting point of slag can be suppressed lower than conventionally, and excellent reduction-generated slag characteristics (metal dripping property) can be realized.

Therefore, when the non-fired carbon-containing lump ore according to one aspect of the present invention is used as a part of the iron-containing raw material for blast furnaces, good air permeability can be realized in the lower part of the furnace during blast furnace operation, and the reduction material ratio (coke ratio) can be greatly reduced. ).

The method for producing a non-fired carbon-containing lump ore for blast furnaces according to one aspect of the present invention uses a non-fired process, and therefore can achieve energy saving and _CO2 reduction compared with a fired process. In addition, dust generated in the iron-making process can be reused as iron-containing raw materials and carbon materials by a relatively cheap and simple method.

Therefore, one aspect of the present invention can be suitably applied to the technical field of carbon-containing lump ore used in a blast furnace.

Claims (7)

1. A non-fired carbon-containing lump ore for blast furnaces, characterized in that it is produced by the following method: iron-containing raw materials, carbon-containing raw materials and binders are mixed, kneaded, and kneaded Forming the object to obtain a formed body, and then curing the formed body, Wherein, the carbon content represented by TC is 18 to 25% by mass, and the ratio CaO/ _SiO2 in the gangue component between the content of CaO in mass % and the content of SiO in mass _% is 1.0 to 2.0, The amount of gangue represented by the following formula (1) is 0.25 or less, Gangue amount = (CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content) (1) Among them, CaO, SiO ₂ , Al ₂ O ₃ and MgO in formula (1) are respectively the content of CaO in mass %, the content of SiO ₂ in mass %, the content of Al ₂ O ₃ in mass %, and the unit is the MgO content in mass %; the carbon content is the amount expressed in TC, and the unit is mass %. 2. The non-fired carbon-containing lump ore for blast furnaces according to claim 1, wherein the MgO content is 0.5% by mass or more. 3 . The non-fired carbon-containing lump ore for blast furnaces according to claim 1 , wherein the content of the binder is 5 to 10% by mass. 4. A method for producing a non-fired carbon-containing lump ore for a blast furnace, characterized in that it has the following steps: A forming process of a molded body, in which the iron-containing raw material, the carbon-containing raw material, and the binder are mixed and kneaded, and the kneaded product is shaped to obtain a molded body; and Next, the process of curing the molded body to obtain a non-fired carbonaceous lump ore, Wherein, the carbon content represented by TC of the non-fired carbon-containing lump ore is 18 to 25% by mass, and the ratio of the CaO content in mass % to the _SiO content in mass % in the gangue component is CaO /SiO ₂ is 1.0 to 2.0, and the amount of gangue represented by the following formula (1) is 0.25 or less, and one selected from the type of ore and the amount of binder is adjusted in the forming process of the molded body. The above matching conditions, Gangue amount = (CaO+SiO ₂ +Al ₂ O ₃ +MgO)/(100-carbon content) (1) Among them, CaO, SiO ₂ , Al ₂ O ₃ and MgO in formula (1) are respectively the content of CaO in mass %, the content of SiO ₂ in mass %, the content of Al ₂ O ₃ in mass %, and the unit is the MgO content in mass %; the carbon content is the amount expressed in TC, and the unit is mass %. 5. The method for producing a non-fired carbon-containing lump ore for a blast furnace according to claim 4, wherein, in the forming The mixing conditions are adjusted in the body forming process. 6 . The method for producing a non-fired carbon-containing lump ore for a blast furnace according to claim 4 , wherein the amount of the binder compounded is adjusted within a range of 5 to 10% by mass. 7. The method for producing a non-fired carbon-containing lump ore for a blast furnace according to claim 4, wherein, in the forming step of the compact, any one of auxiliary raw materials and high _SiO2- containing ores is further blended Or or both, the auxiliary raw material is selected from silica, serpentine, olivine, dolomite, nickel slag, magnesite, brucite, Wherein, the non-fired carbon-containing lump ore has a carbon content represented by TC of 18 to 25% by mass and a ratio of CaO content to SiO content of 1.0 to _{2.0 (CaO/SiO 2 )} . The compounding amount of high SiO ₂ ore.

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