JP5000402B2 - Method for producing carbon-containing unfired pellets for blast furnace - Google Patents

Description

  The present invention is a fine powder comprising iron-containing dust such as sintered dust and blast furnace dust generated in the iron making process, and fine iron ore such as pellet feed (raw material for pellets) having a smaller particle size than the powder iron ore for sintering. The present invention relates to a method for producing a carbon-containing unfired pellet for a blast furnace, in which an iron-containing raw material and a pulverized carbon material are granulated and produced.

  The iron raw material for blast furnaces in the current iron making process uses powdered iron ore with an average particle size of about 2 to 3 mm as the main iron-containing raw material, and contains auxiliary materials such as limestone and silica, and carbonaceous materials such as powdered coke and anthracite. In addition, sintered ore obtained by adding water and mixing and granulating into pseudo particles and then heating and sintering the carbonaceous material in the raw material with a sintering machine as the heat source dominates.

  The granulated product of the sintered raw material in this method is a pseudo particle in which fine particles having a particle size of less than about 0.5 to 1 mm are attached around the coarse particles having a particle size of about 1 mm or more as a core. . In order to maintain the breathability of the sintering raw material in the sintering machine and to advance the sintering reaction satisfactorily, these pseudo particles are heated and dried and sintered in order to advance the sintering reaction well. The cold crushing strength that does not collapse is required.

  Usually, in order to granulate a sintering raw material into pseudo particles, granulation is often performed together with mixing of the sintering raw material using a drum mixer.

  On the other hand, iron-containing dust collected by a dust collector, etc., which is a large amount of sintered dust, blast furnace dust, etc. generated in the iron making process, fine dust such as sludge and scale powder (these are generally called iron making dust), pellets Fine powder materials such as feed (raw materials for pellets) are also used as iron-containing materials.

  However, in these fine powder raw materials, fine powder particles having a particle size of 0.25 mm or less occupy 80% or more of the total, so when these are used as a sintering raw material, the permeability of the raw material packed layer is deteriorated due to the fine powder particles, production It is easy to cause problems such as deterioration of performance.

  When sintering such a fine powdery raw material as a main iron-containing raw material, after adding water to the iron-containing raw material and auxiliary raw materials and mixing them in advance using a mixer, granulation is further performed compared to a drum mixer. Using a granulator such as a disk pelletizer with high strength to produce spherical pellets mainly composed of fine particles with a particle size of 0.25 mm or less, and then using an external heating type sintering machine that uses combustion gas as a heat source Sintering is performed.

  In addition, after the granulated raw material is granulated into pellets, the strength of the granulated material is increased by curing (hydration reaction or carbonation treatment of quick lime etc.), and then it is used as it is for blast furnace without sintering. Non-calcined agglomerates used as iron raw materials have also been known for a long time.

  As a method for producing non-calcined agglomerated ore, the particle size distribution of dust is appropriate when pelletizing iron dust generated at steelworks such as blast furnace secondary ash, converter dust, sintered dust, and slurry. Adjust to the range, add binder (binder) such as quick lime and cement and 5-15% moisture, granulate with a disk pelletizer, etc. to produce pellets, then cure for several days by yard deposition (CaO binder) There is known a method for producing cold bond pellets that are cured by promoting hydration reaction and carbonation reaction (for example, see Patent Document 1).

  In recent years, for the purpose of reducing the ratio of reducing materials in blast furnace operation, a method for producing a non-fired agglomerate having a high carbon content using the non-fired agglomerate process has also been proposed (for example, Patent Documents 2 to 5).

For example, to reduce iron oxide in iron ore to metallic iron in a carbon interior non-fired agglomerate that is made by mixing iron-containing iron oxide raw material and carbon-based carbonaceous material and kneading, molding and curing by adding a binder. The binder is selected, mixed, molded, and cured so that it contains 80 to 120% of the theoretical amount of carbon necessary for the process, and the crushing strength at room temperature is 7850 kN / m ² (80 kg / cm ² ) or higher. A carbon interior non-fired agglomerated ore for blast furnace and a method for producing the same have been proposed (see, for example, Patent Document 2).

According to this method, the thermal preservation zone and reduction of the blast furnace shaft part, in which the progress of the reduction reaction of iron oxide is generally restricted from the relationship between the temperature of the reducing gas and the gas composition (ηCO = CO ₂ / (CO + CO ₂ )). Even in the reaction equilibrium zone, in the temperature range of 900 to 1100 ° C., the iron oxide in the uncalcined agglomerate undergoes a reduction reaction due to the carbon incorporated therein, and as a result, the reduction rate is improved, so the ratio of reducing materials during blast furnace operation The reduction effect can be expected.

  However, in this method, the C content contained in the unfired agglomerated mineral is 120% or less in terms of the theoretical carbon amount (hereinafter sometimes referred to as C equivalent) necessary for reducing the oxide ore into metallic iron. The total carbon content (TC) is limited to about 15% by mass or less), and if the C content is further increased, the cold crushing strength and hot strength of the unfired agglomerated minerals are impaired. There was a problem.

  Furthermore, in this method, in order to maintain the cold crushing strength of the unfired agglomerated minerals with the carbonaceous material, a cement-based binder such as early-strength Portland cement is used instead of quick lime. Increasing the amount not only reduces the rate of temperature rise at the shaft in the blast furnace due to the dehydration reaction of cement, which is an endothermic reaction, but also generates a reduction stagnation zone (low temperature thermal preservation zone) at low temperatures, which causes iron for blast furnaces. The problem was that it promoted reducing powderization in the blast furnace of the sintered ore charged as a raw material.

  In addition, it is a coal interior pellet made of iron ore mainly composed of carbon material and iron oxide, and defines the relationship between the maximum fluidity during softening and melting of the carbon material and the ratio of iron oxide particles of 10 μm or less in the iron ore. Carbonaceous material-incorporated pellets excellent in reducing properties and strength after reduction have been proposed (see, for example, Patent Document 3).

  According to this method, the carbonaceous material in the pellets is softened and melted and solidified in a temperature range of 260 to 550 ° C., and the molten carbonaceous material enters and solidifies into the voids between the iron oxide particles. By increasing the contact area of iron oxide, improving thermal conductivity to increase reduction efficiency, and strengthening the bond between iron oxide particles, the strength after reduction (hot strength) can also be improved.

  However, in order to improve the reducibility and strength after reduction (hot strength) of the carbon material-containing pellets by this method, coal with the highest fluidity must be used as the carbon material. It is difficult to say that this is a preferable method from the viewpoint of reducing the reducing material ratio during blast furnace operation on the premise of saving resources.

Also, after mixing powdered ore and caking coal (carbon material) having a volatile content of 16% or more and a Gieseler fluidity of 20 DDPM or more and hot forming at a molding pressure of 20 to 150 MPa in a temperature range of 260 to 550 ° C. An agglomerated product for reduced iron having an apparent density of 2.3 g / cm ³ or more, characterized by performing a degassing treatment for 5 minutes or more in a molding temperature range (see, for example, Patent Document 4). ).

According to this method, hot molding is performed in a temperature range of 260 to 550 ° C. where the carbon material is softened, melted and solidified, and the iron oxide particles are firmly connected with the carbon material, and the apparent density is 2.3 g / cm ^3. After the above-mentioned agglomerated material is obtained, the volatile matter from the carbonaceous material is removed by degassing, thereby increasing the strength of the agglomerated material and preventing cracking due to swelling of the agglomerated material during reduction.

However, since this method requires hot briquette molding and degassing treatment, it is an economically disadvantageous method in terms of high energy consumption during production and high production costs. Since the density of the agglomerate is higher than that of, explosions (bursting) due to CO and CO ₂ gas generated by the gasification of the carbonaceous material in the agglomerate and the reduction reaction of iron oxide are likely to occur.

  Also, a carbon material having a particle size of 3 to 25 mm is used as a core, and an outer peripheral layer including the core is a mixture of an iron raw material and a carbon material having a particle size of 1 mm or less, and the volume fraction of the carbon material as the core is agglomerated. It is 0.2-30 vol% of the whole ore, the content rate of the carbonaceous material in the outer peripheral layer is 5-25 wt%, and the total carbon content of the entire agglomerated ore is as high as 25-35 mass%. A carbonaceous material agglomerate has been proposed (see, for example, Patent Document 5).

  According to this technique, when reducing the iron oxide with a carbonaceous material having a particle size of 1 mm or less contained in the outer peripheral layer, and the outer peripheral layer is melted, by making the carbonaceous material as a nucleus function as a carburizing source, In addition to improving the reducibility in the blast furnace, the dripping behavior of the hot metal due to the carburizing action can be improved, and the fuel ratio can be reduced during the blast furnace operation and the ventilation resistance of the cohesive zone can be reduced.

  However, the agglomerates having a double structure in which the particle size and the composition of the carbonaceous material and the oxide are different and the total carbon content is as high as 25% by mass or more have a problem that the cold wear strength is low. In addition, in order to manufacture such agglomerates having a special double structure, the manufacturing process becomes complicated, and a large amount of binder is required to maintain strength. It was a disadvantageous method.

As described above, the conventional carbon-containing non-fired pellets have a carbon content of 15% by mass (1.2% in terms of carbon equivalent) in order to maintain the cold crushing strength of 50 kg / cm ² or more required as a blast furnace raw material. Therefore, the direct reduction of iron oxide in the pellets can be sufficiently promoted, but the reduction of major blast furnace iron-containing raw materials such as sintered ore other than the pellets is sufficient. It could not be promoted.

  Also, by adding a large amount of hydraulic binder such as Portland cement by the conventional method, the cold crushing strength of the carbon-containing unfired pellets can be improved to some extent, but the binder is dehydrated in the reduction temperature range in the blast furnace. Due to the reaction, sufficient hot strength could not be maintained.

  Therefore, in order to improve the reduction rate of carbon-containing unfired pellets and iron-containing raw materials for blast furnace using a relatively inexpensive and simple manufacturing method, and to greatly reduce the ratio of reducing material during blast furnace operation, Development of a method for producing unfired agglomerates of carbonaceous materials with an excellent carbon content and excellent cold strength as well as hot strength in the reduction temperature range (strength during reduction) is desired. .

JP-A-53-130202 JP 2003-342646 A JP 2000-160219 A JP 11-92833 A JP-A-8-199249

In view of the present state of the prior art, the present invention uses not only carbon-containing unfired pellets but also other major iron-containing raw materials for blast furnaces when used in a blast furnace using a relatively inexpensive and simple manufacturing method. Has sufficient carbon content to greatly reduce the ratio of reducing material during blast furnace operation and maintains the cold crushing strength of 50 kg / cm ² or more required as a blast furnace raw material. It is an object of the present invention to provide a method for producing a carbon-containing non-fired pellet that is superior in hot strength in the reduction temperature range as compared to the conventional case.

  The present inventors have a structure of filling raw material particles constituting carbon-containing unfired pellets, behavior of raw material particles in a reduction temperature range in a blast furnace (carbon material, pyrolysis and gasification of binder, and iron oxide particles). The relationship between the reduction state) and the cold strength of the pellets and the hot strength in the reduction temperature range was studied intensively through experiments and the like.

  As a result, among the raw material particles in the carbon-containing non-fired pellets, in particular, the carbonaceous material particle size (mass-based median diameter) and carbon content are reduced in the reduction temperature range along with the cold strength of the carbon-containing non-fired pellets. It has been found that this greatly affects the hot strength.

  The present invention has been made to solve the above problems based on this finding, and the gist of the present invention is as follows.

(1) Add a hydraulic binder to a finely divided iron-containing raw material containing 40 mass% or more of iron and a finely divided carbonaceous material containing 10 mass% or more of carbon, and mix and granulate while adjusting moisture. This is a method for producing a blast furnace carbon-containing unfired pellet having a cold crushing strength of 50 kg / cm ² or more, wherein the particle size of all raw materials is 2 mm or less, and the carbon content ratio (TC) in all raw materials is Adjusting the blending ratio of the pulverized carbon material so as to be 15 to 25% by mass, and the median diameter of the pulverized carbon material is 100 to 150 μm, Production method.

  (2) Addition of 5 to 15% by mass of the hydraulic binder, and granulate while adjusting the water content to 5 to 15% by mass. Pellet manufacturing method.

  (3) The blast furnace inclusion according to (1) or (2) above, wherein any one or more of blast furnace primary ash, coke dust, and powder coke are used as the finely divided carbonaceous material. A method for producing charcoal non-fired pellets.

  (4) The blast furnace according to any one of (1) to (3) above, wherein one or more of sintered dust and fine iron ore are used as the fine iron-containing material. Of manufacturing carbon-containing non-fired pellets.

  (5) The pulverized iron-containing raw material is mixed with pulverized iron ore, and ultrafine particles having a particle size of 10 μm or less are contained in the iron ore in a proportion of 3.5% by mass or more with respect to the total raw material. The manufacturing method of the carbon-containing non-baking pellet for blast furnaces in any one of said (1)-(4).

  (6) The said (1)-(5) characterized by adjusting the mixture ratio of the said fine powder carbon material so that the carbon content rate (TC) in the said all raw materials may be 15-20 mass%. ) For producing a carbon-containing non-fired pellet for a blast furnace.

According to the present invention, when used in a blast furnace, it has a sufficient carbon content to improve the reduction rate of not only carbon-containing unfired pellets but also main blast furnace iron-containing raw materials such as sintered ore. In addition, while maintaining the cold crushing strength of 50 kg / cm ² or more required as a raw material for blast furnaces, the manufacture of carbon-containing non-fired pellets that are superior in hot strength in the reduction temperature range as compared with the past. Can do.

  Therefore, by using the carbon-containing unfired pellets obtained by applying the present invention as a part of the iron-containing raw material for blast furnace, the reducing material ratio (coke ratio) during blast furnace operation can be greatly reduced. .

Furthermore, using the non-fired pellet process that enables energy saving and lower CO ₂ compared to the firing process, the dust generated in the iron making process can be reduced by using a relatively inexpensive and simple method. Since it can be recycled as a material, industrial and social contributions are significant.

  Details of the present invention will be described.

  The method for producing a carbon-containing non-fired pellet for a blast furnace according to the present invention includes adding a hydraulic binder to a finely divided iron-containing raw material containing 40 mass% or more of iron and a finely divided carbonaceous material containing 10 mass% or more of carbon. And granulation while adjusting the moisture.

  The pulverized iron-containing raw material containing 40% by mass or more of iron and the pulverized carbon material containing 10% by mass or more of carbon are not particularly limited. For example, in the iron making process shown in Table 1 and FIG. In addition to the raw materials used, iron-making dust generated in each manufacturing step of the iron-making process can be used.

  Table 1 and FIG. 1 show the main components and particle size distribution of various pulverized iron-containing raw materials and pulverized carbonaceous materials.

  In addition, the raw material particle size in a table | surface was represented by the mass median diameter. The mass-based median diameter is defined as the particle diameter of the raw material corresponding to a cumulative value (mass%) of 50% in the cumulative mass distribution of the raw material particles.

  In general, the particle size distribution characteristic of the raw material is often a mass average diameter, but even in the case of a raw material having the same particle size distribution characteristic, the value varies depending on how to take the class. A mass-based median diameter with high accuracy was adopted as an index of raw material particle size.

  In the present invention, the sintered dust and fine iron ore shown in Table 1 and FIG. 1 are used as a fine powder iron-containing raw material containing 40% by mass or more of iron, and blast furnace primary ash, coke dust, and fine coke are used. It can be used as a finely divided carbonaceous material containing 10% by mass or more of carbon.

  Further, as shown in Table 1 and FIG. 1, since the particle size varies depending on each iron-making dust and each iron-making raw material, the particle size of the whole raw material and the particle size (mass-based median diameter) of the pulverized carbonaceous material described later are within a predetermined range. In order to adjust the particle size, it is preferable to adjust the blending amount of each ironmaking dust and each ironmaking raw material, and further adjust the particle size by sieving, crushing, washing with water and the like.

  The granulation equipment is not particularly limited, and may be any material having functions of kneading raw materials, hydration, granulation, and product sieving. Kneading machines, granulating machines, etc. are not particularly limited. Absent.

  In the present invention, the hydraulic binder means a binder having a function of increasing the cold crushing strength of the granulated product by curing by a hydration reaction with moisture contained in the raw material or added moisture. The kind of binder is not specifically limited.

  Examples of such hydraulic binders include aging binders composed of fine powder mainly composed of blast furnace granulated slag and alkali stimulants, Portland cement, bentonite, and the like in the present invention. Can be used.

The present invention has a carbon content that can greatly reduce the ratio of reducing material during blast furnace operation: 15 mass% (corresponding to 1.2 in terms of carbon equivalent) or more, a cold crushing strength of 50 kg / cm ² or more, The second premise is to produce a carbon-containing non-fired pellet that is superior in hot strength in the reduction temperature range as compared to the conventional case.

  Conventionally, the ratio of the carbon content (TC) to the theoretical carbon amount required to reduce iron oxide in a carbon-containing unfired pellet is defined as “carbon equivalent”, and reduction of iron oxide by carbon It is a guideline for the degree.

  The carbon content of the present invention: 15% by mass or more corresponds to a carbon equivalent of 1.2 or more. When used in a blast furnace, the iron oxide in the non-fired pellets is reduced, and the excess carbon is gasified. Thus, it can be expected that the reduction of iron-containing raw materials for blast furnaces such as sintered ore other than non-fired pellets will be promoted.

  However, as mentioned above, according to the conventional granulation method, unless a large amount of special granulation or binder is added, the cold crushing strength of the carbon-containing unfired agglomerated ore greatly decreases, The amount could not be increased beyond 15% by mass (corresponding to 1.2 in terms of carbon equivalent).

  Moreover, by adding a large amount of a hydraulic binder such as Portland cement, the cold crushing strength of the carbon-containing non-fired pellets can be improved to some extent, but the binder causes a dehydration reaction in the reduction temperature range in the blast furnace. Therefore, sufficient hot strength cannot be maintained.

  Therefore, the present inventors have made the structure of the carbon-containing unfired pellets in the cold and reduction temperature range and the behavior of the raw material particles in the blast furnace (carbon material, pyrolysis and gasification of the binder, and iron oxide particles). The relationship between the reduction state) and the strength in the cold and reduction temperature range was examined by reduction test and crushing strength measurement.

Using a reduction test device that can simulate the reduction reaction in the blast furnace under load, the reducing gas composition in the thermal storage zone and reduction reaction equilibrium zone of the blast furnace shaft (CO is 36%, CO ₂ is 14%, N ₂ is 50% ) And temperature (900 to 1100 ° C.) under almost the same conditions, a reduction test was performed using carbon-containing non-fired pellets (carbon equivalent: 2.0) with a carbon content (TC) of 20% by mass.

  For carbon-containing non-fired pellets, the raw materials are mixed for 5 minutes with a mixer, 10% by weight of Portland cement is added, and then kneaded for 5 minutes with a kneader and then granulated with a granulator. And it was set as the raw pellet. As the sample, the raw pellet was further left in the room for 2 weeks (curing treatment). Reduction temperature: Samples reduced at 900 ° C. and 1100 ° C. were taken out from the reduction test apparatus, the structure was observed, and the crushing strength was measured.

The crushing strength is measured in accordance with JIS M8718 by measuring the load value when one sample is broken by applying a compressive load at a specified pressure rate. Load value (kg / cm ² ).

  FIG. 2 schematically shows the process of state change of each raw material particle (iron oxide, carbonaceous material, cement (binder)) in the carbon-containing unfired pellets in the cold and reduction temperature range based on the above test results. .

The raw material particle structure of the carbon-containing non-fired pellets before the reduction has a structure in which the gap between the iron oxide particles and the carbon material particles is filled with cement (binder) and is firmly bonded, so that the crushing strength is 50 kg / cm. A cold strength of ² or more can be maintained.

  From the experimental results of the present inventors, as conventionally known, when the carbon content ratio in the carbon-containing unfired pellets is excessively high, or when the particle size of all raw materials is excessively large, It has been confirmed that the crushing strength decreases.

  The cold strength of the carbon-containing unfired pellets is improved to some extent by increasing the carbon content within a predetermined range or increasing the amount of cement (binder) added in accordance with the increase in the particle size of all raw materials. However, as will be described later, in the high temperature region in the blast furnace, carbon and the binder are gasified, voids are formed, causing a decrease in hot strength, so an excessive increase in the content ratio of carbon and binder is not preferable. .

  On the other hand, at a reduction temperature of 900 ° C. corresponding to the lower limit temperature of the heat preservation zone of the blast furnace shaft portion, the cement disappears due to a dehydration reaction that occurs on a lower temperature side than this temperature, and thereafter voids are formed.

  At this reduction temperature, among the carbonaceous materials, the carbonaceous material particles having a large particle size remain as they are, but the carbonaceous material having a small particle size (about 50 μm or less) is gasified to CO at a relatively low temperature and disappears. At the same time, it was found that as a result of the reduction of iron oxide by CO gas, a network phase of metallic iron in which the produced metallic irons are bonded to each other is formed.

At this reduction temperature, the crushing strength is about 11 kg / cm ² despite the disappearance of the cement (binder) that binds iron oxide and carbon in the cold state. Limiting crush strength under conditions: Sufficient strength exceeding 10 kg / Piece (equivalent to 7 kg / cm ² for a particle size of 13 mm) (for example, iron and steel, 72 (1986), p. S980, see)) .

  Reduction temperature: At 900 ° C., the network phase of metallic iron formed by the reduction reaction of iron oxide with a carbonaceous material with a small particle size (about 50 μm or less) is the movement of vacancies like oxides and diffusion of anions It is considered that the spot-like metallic irons are formed by solid-phase diffusion bonding at an extremely high diffusion rate without accompanying.

  The network phase of metallic iron formed in this way has a sufficiently large resistance to the load caused by the charges in the blast furnace even at high temperatures, thus preventing the softening and fusion of the sintered layer in the blast furnace. Thus, the breathability is greatly improved. Further, at this reduction temperature, the reduction rate of the carbon-containing non-fired pellets reaches 95%, which is a reduction rate that can be reached when reducing iron oxide by only gas reduction.

  At a reduction temperature of 900 ° C., the carbonaceous material having a coarse diameter (about 50 μm or more) in the pellet has a smaller surface area than the carbonaceous material of fine powder (about 50 μm or less), so the gasification reaction is delayed. Remains in.

  Furthermore, from the upper limit temperature of the heat preservation zone of the blast furnace shaft portion, the reduction temperature corresponding to the reduction reaction equilibrium zone: 1100 ° C., the reduction material temperature: 900 ° C. The remaining carbon particle having a large particle size (about 50 μm or more) is also gas It disappeared by the chemical reaction. At a reduction temperature of 900 ° C., the reduction rate of the carbon-containing non-fired pellets has already reached 95%. Therefore, the carbonized material gasified at this reduction temperature is used for sintered ore other than the pellets, lump ore, etc. It can be expected to be used for the indirect reduction reaction of the main iron-containing raw materials for blast furnace.

Further, at this reduction temperature, the network phase of metallic iron formed at the reduction temperature: 900 ° C. is maintained, the crushing strength is about 11 kg / cm ² , and the strength equivalent to the reduction temperature: 900 ° C. is maintained. ing.

  In addition, at the reduction temperatures: 900 ° C. and 1100 ° C., the strength is maintained by the network phase between the metal irons, but as will be described later, when the carbon content ratio with respect to all the raw materials in the pellet becomes excessively high, Since the interval between the iron oxide particles is increased, the formation of the network phase between the metal irons is hindered, which causes a decrease in hot strength at reduction temperatures of 900 ° C. and 1100 ° C.

  Moreover, in the case of a carbon-containing non-fired pellet containing only a carbonaceous material having a small particle size (about 50 μm or less), most of the iron oxide is reduced to a metallic iron by a reduction reaction with the carbonaceous material at a relatively low temperature of 900 ° C. or higher. Even after this, gasification of the carbonaceous material proceeds and voids are generated in the pellet, so that the pellet crushing strength in the high temperature range at 900 to 1100 ° C. is greatly reduced.

The present invention has been made based on the above findings, and by optimizing the particle size of all raw materials, the carbon content ratio (TC) in all raw materials, and the median diameter of finely divided carbonaceous materials, Cold crushing strength required as a raw material for blast furnace: Maintaining 50 kg / cm ² or more, mainly in the thermal preservation zone temperature range (900 ° C. or more) of the blast furnace shaft part, mainly by the reduction reaction of iron oxide by fine-grained carbon. It promotes the formation of metallic iron network phase in the pellet, and in the reduction reaction equilibrium zone temperature range (below 1100 ° C) of the blast furnace shaft, the main (main) blast furnace iron other than the residual (coarse) carbon in the pellet and the pellet Promote indirect reduction of contained raw materials (sintered ore, lump iron ore, etc.) to produce carbon-containing non-fired pellets with higher reducibility and superior hot strength in the reduction temperature range Technical thought to do It is intended to.

In order to realize the above technical idea, the constitution of the present invention is to add a hydraulic binder to a finely divided iron-containing raw material containing 40% by mass or more of iron and a finely divided carbonaceous material containing 10% by mass or more of carbon. And by granulating while adjusting the moisture, assuming a method of producing coal-free non-fired pellets for blast furnace with a cold crushing strength of 50 kg / cm ² or more, the particle size of all raw materials is 2 mm or less, The blending ratio of the fine powdery carbonaceous material is adjusted so that the carbon content ratio (TC) is 15 to 25% by mass, and the median diameter of the fine powdery carbonaceous material is 100 to 150 μm. And

  Below, the reason for limitation of the structure characterized by this invention is demonstrated.

(Particle size of all raw materials, carbon content ratio (TC), median diameter of pulverized carbonaceous material)
FIG. 3 shows the relationship between the median diameter and carbon content (TC) of the finely divided carbonaceous material in the pellet and the crushing strength after reduction at a reduction temperature of 1000 ° C.

  Moreover, in FIG. 4, the relationship between the median diameter and carbon content rate (TC) of the pulverized carbonaceous material in a pellet and the reducing material ratio at the time of blast furnace operation is shown.

  The raw materials are sintered dust and fine iron ore shown in Table 1 as fine powdered iron-containing raw materials, blast furnace primary ash, coke dust and fine coke are finely divided carbonaceous materials, and early-strength Portland cement is used as a binder. Was adjusted to 2 mm or less, and pellet granulation and curing were performed in the same manner as in the method and conditions described in FIG.

  The crushing strength shown in FIG. 3 is the same reduction test method and conditions as used in FIG. 2, and the carbonized non-fired pellets with different carbonaceous material content and carbonaceous particle size reduced at a reduction temperature of 1000 ° C. are taken out. The crushing strength was measured by the same method as that used in FIG.

  Further, the ratio of reducing materials during blast furnace operation shown in FIG. 4 is obtained by using a test apparatus (BIS furnace) capable of simulating a reduction reaction in the blast furnace, and using a part (10% by mass) of ordinary sintered ore as charcoal. The result which evaluated the reducing material ratio (RAR) when it replaces with the non-baking pellet from which material content and a carbon material particle size differ is used in a blast furnace is shown. In addition, the non-baked pellets were uniformly dispersed in the ore layer in the test apparatus (BIS furnace). The reducing material ratio (RAR) was calculated using a list diagram based on the exhaust gas analysis result in the steady state.

  According to FIG. 3, it can be seen that the crushing strength is lowered regardless of whether the particle size (median diameter) of the carbonaceous material is small or too large in any carbon content (TC) of any pellet. This is because if the particle size of the carbon material is too small, the carbon material contained in it is gasified in a large amount before the bridging effect due to reduction of iron oxide to metal is sufficiently expressed at a low temperature, resulting in a large amount of voids, This indicates that sufficient strength cannot be maintained.

  On the other hand, if the particle size of the carbon material is too large, the gasification reaction is delayed, the reduction of iron oxide is delayed, and the production of metallic iron becomes non-uniform, so that the cement bond in the pellet is not enough before disappearing. This is because a network phase of metallic iron cannot be formed.

  Further, even when the carbonaceous material has the same particle size (median diameter), the greater the carbonaceous material content, the smaller the crushing strength after reduction. This is because as the carbon content (TC) increases, the average distance between iron oxide particles increases, and the voids formed after gasification of the carbonaceous material and binder (cement) increase. This is because the formation of an iron network phase is inhibited.

  In addition, in FIG. 3, the crushing strength of pellets having a reduction temperature of 1000 ° C., in which the particle size of all raw materials is adjusted to 5 mm or less, in addition to the pellets in which the particle size of all raw materials is adjusted to 2 mm or less, is indicated by ●. From the figure, it can be seen that the crushing strength of pellets having a reduction temperature of 1000 ° C., in which the particle size of all raw materials is adjusted to 5 mm or less, is significantly lower than that of pellets in which the particle size of all raw materials is adjusted to 2 mm or less.

  This is because a coarse carbon material with a particle size of 2 mm or more has a slow gasification reaction, so that the network phase of metallic iron does not develop sufficiently, and the compressive stress due to the load of the charge is gasified. This is because it concentrates on the remaining carbon material and coarse raw material particles such as coarse iron oxide and becomes the starting point of destruction.

According to FIG. 3, in order to ensure a limit crushing strength of 7 kg / cm ² or more that can maintain the pellet's self-shape against the load of the charge in the blast furnace, It is understood that it is necessary to set the carbon content (TC) to 25% by mass or less, and to set the particle size (median diameter) of the carbonaceous material within the range of 100 to 150 μm.

  According to FIG. 4, it can be seen that, regardless of the carbon content (TC) of any pellet, the reducing material ratio (RAR) during blast furnace operation decreases as the particle size (median diameter) of the carbon material decreases. In addition, it can be seen that the reducing material ratio (RAR) at the time of blast furnace operation decreases as the carbon content (TC) of the pellet increases even under the same condition of the particle size (median diameter) of the carbonaceous material.

The reason for this is that as the particle size (median diameter) of the carbon material decreases and the carbon content (TC) of the pellet increases, the gasification reactivity increases. In addition to promoting the reduction of iron oxide, the temperature of the heat preservation zone at the blast furnace shaft portion is reduced, and the iron wustite and equilibrium gas composition move to the low reduction potential side, so the efficiency of use of the reducing gas (ηCO = CO ₂ / (CO + CO ₂ )) is improved.

  In FIG. 4, the carbon content (TC) of the 14 mass% pellet is the carbon equivalent (the carbon content relative to the theoretical carbon amount required to directly reduce iron oxide in the carbon-containing unfired pellet ( The ratio of TC) corresponds to 1.0, but at this carbon content, the carbonaceous material is almost consumed for direct reduction of the iron oxide in the pellet itself, so the ratio of reducing material during blast furnace operation (RAR) ) Reduction effect is small.

  According to FIG. 4, when the carbon content (TC) is 15% by mass or more, an effect of reducing the reducing material ratio (RAR) during blast furnace operation is obtained, in addition to direct reduction of iron oxide in the pellet itself, It can be seen that gasification of surplus carbon promotes indirect reduction of main blast furnace iron-containing raw materials such as sintered ore adjacent to non-fired pellets.

  On the other hand, even if the carbon content (TC) is 15% by mass or more, if the carbonaceous material particle size (median diameter) becomes coarser than 150 μm, the carbonaceous material particle size is too large. Since the gasification reaction does not proceed sufficiently, the reducing material ratio (RAR) reduction effect during blast furnace operation is small.

  Further, in FIG. 4, the crushing strength of pellets having a reduction temperature of 1000 ° C., in which the particle size of all the raw materials is adjusted to 5 mm or less, in addition to the pellets in which the particle size of all the raw materials is adjusted to 2 mm or less, is indicated by ●. From the figure, compared with the pellets in which the particle size of all raw materials was adjusted to 2 mm or less, in the pellets in which the particle size of all raw materials was adjusted to 5 mm or less, the reducing material ratio (RAR) reduction effect during blast furnace operation was significantly impaired. I understand that.

  This is because a coarse carbon material having a particle size larger than 2 mm has a slow gasification reaction, so that indirect reduction of main blast furnace iron-containing raw materials such as sintered ore cannot be sufficiently promoted.

  According to FIG. 4, in order to sufficiently reduce the reducing material ratio (RAR) during blast furnace operation to 475 (kg / tp) or less, the particle size of all raw materials is set to 2 mm or less, and the carbon content (TC ) Must be 15% by mass or more, and the particle size (median diameter) of the carbonaceous material must be within a range of 150 μm or less.

  As described above with reference to FIGS. 3 and 4, when the particle size of all raw materials exceeds 2 mm, the carbonaceous material has a slow gasification reaction, so that the network phase of metallic iron cannot be sufficiently developed. Since the indirect reduction of the main blast furnace iron-containing raw materials such as sintered ore cannot be sufficiently promoted, neither the crushing strength nor the reducing material ratio (RAR) during blast furnace operation can be sufficiently improved.

When the carbon content (TC) is less than 15% by mass, the gasification reactivity is lowered, so that the reduction of the iron oxide in the non-fired pellets is promoted and the temperature of the heat preservation zone at the blast furnace shaft portion is lowered. However, since the use efficiency (ηCO = CO ₂ / (CO + CO ₂ )) of the reducing gas cannot be sufficiently improved, the reducing material ratio (RAR) at the time of blast furnace operation cannot be sufficiently improved.

  Conversely, if the carbon content (TC) exceeds 25% by mass, the average distance between the iron oxide particles increases, and the formation of the metallic iron network phase is hindered. It cannot be improved.

  When the particle size (median diameter) of the carbonaceous material is less than 100 μm, the carbonaceous material cannot be present in a close-packed structure, and the crushing strength is reduced. On the other hand, if the particle size (median diameter) of the carbon material exceeds 150 μm, the gasification reaction will be slow, the reduction of iron oxide will be delayed, and it will not be possible to form a sufficient metallic iron network phase. Cannot be improved sufficiently.

Further, when the particle size (median diameter) of the carbonaceous material is less than 100 μm, the effect of improving the gasification reactivity due to the increase in the specific surface area is reduced, so that the reduction of the iron oxide in the non-fired pellets is promoted and the blast furnace shaft portion As the heat storage zone temperature of the steel decreases, the effect of reducing gas utilization efficiency (ηCO = CO ₂ / (CO + CO ₂ )) is lost, so the ratio of reducing material (RAR) during blast furnace operation is sufficiently improved. I can't do it.

For the above technical reasons, in the present invention, a minimum crushing strength of 7 kg / cm ² that can maintain the self-shape of the pellet with respect to the load of the charged material in the blast furnace is secured, and the blast furnace In order to sufficiently reduce the reducing material ratio (RAR) during operation to 475 (kg / tp) or less, the particle size of all raw materials is 2 mm or less, the carbon content (TC) is 15 to 25% by mass, And the particle size (median diameter) of a carbon material is prescribed | regulated as 100-150 micrometers.

As described above, the cold crushing strength of the carbon-containing non-fired pellets having a crushing strength of 7 kg / cm ² or more in the temperature range (900 to 1100 ° C.) from the thermal preservation zone of the blast furnace shaft portion to the reduction reaction equilibrium zone. Can secure 50 kg / cm ² or more.

  Therefore, the carbon-containing non-fired pellets of the present invention have a cold strength that can sufficiently withstand the damage caused by impact during transportation and charging in the blast furnace, so that during handling, transportation to the blast furnace, and charging, There is no worry about conversion.

  The carbon-containing non-fired pellets of the present invention have a high carbon content (TC) and a low apparent density as compared with ordinary non-fired pellets. There is a concern that it will be segregated at the top of the main raw material containing blast furnace iron.

  In the temperature range (900 to 1100 ° C.) from the thermal preservation zone of the blast furnace shaft portion to the reduction reaction equilibrium zone, CO gas generated by the gasification of the carbonaceous material in the carbon-containing unfired pellets of the present invention is converted into the surrounding sintered ore. From the standpoint of efficient use for reduction of steel, non-fired pellets with a high carbon content are placed in the lower layer of the ore layer and are usually reduced with a gas whose reduction potential has been reduced by reduction of the sintered ore in the lower layer. It is necessary to promote reduction of the upper-layer sintered ore.

  FIG. 5 shows the relationship between the carbon content (TC) in the carbon-containing non-fired pellets and the occupation ratio at the height direction position of the sintered ore layer thickness.

  In addition, FIG. 5 is a blast furnace charging simulator. After charging a coal-containing non-fired pellet having a different carbon content (TC) from the sintered ore, the carbon-containing non-fired in the height direction position of the sintered ore layer thickness. It is the result of having measured the occupation rate of the pellet.

  The carbon-containing non-fired pellets were produced using the raw materials shown in Table 1 under the same methods and conditions as those used in FIG. Moreover, the sintered ore imitated an actual machine and had a particle size range of 50 mm or less, an average particle size of 15 mm, and the carbon-containing non-fired pellets had an average particle size of 10 to 15 mm.

According to FIG. 5, it can be seen that as the carbon content (TC) of the carbon-containing non-fired pellets increases, the carbon-containing non-fired pellets are unevenly distributed in the upper layer of the sintered ore layer after charging. This is because the apparent density of the sintered ore is 2.8 g / cm ³ , whereas the apparent density of the carbon-containing non-fired pellets increases as the carbon content (TC) of the carbon-containing non-fired pellets increases. However, it is because it becomes relatively small. The apparent density of the carbon-containing non-fired pellets having a carbon content (TC) of 25% by mass or less is maintained at 2.0 g / cm ³ , and the influence of the difference from the average particle diameter with the sintered ore is also affected. Yes, it is possible to uniformly charge the sintered ore layer.

  From the above, in the present invention, by setting the carbon content (TC) of the carbon-containing unfired pellets to 25% by mass or less, excessive segregation in the sintered ore layer of the carbon-containing unfired pellets during charging of the blast furnace. In the temperature range (900-1100 ° C.) from the thermal preservation zone of the blast furnace shaft to the reduction reaction equilibrium zone, the CO gas generated by the carbonaceous material in the pellets of the iron-containing raw material for main blast furnaces such as sintered ore It is possible to contribute to the promotion of indirect reduction.

  During charging of the blast furnace, segregation in the sintered ore layer of the carbon-containing unfired pellets is suppressed, and CO gas generated by the carbonaceous material in the carbon-containing unfired pellets reduces the other main blast furnace iron-containing raw materials. From the point of promotion, it is more preferable that the carbon content (TC) of the carbon-containing non-fired pellets is 20% by mass or less.

(Amount of hydraulic binder added, water content)
As described above, the present invention adds a hydraulic binder to a finely divided iron-containing raw material containing 40% by mass or more of iron and a finely divided carbonaceous material containing 10% by mass or more of carbon, while adjusting moisture. On the premise of producing granulated non-fired pellets for blast furnace with a cold crushing strength of 50 kg / cm ² or more by granulation, the amount of hydraulic binder added and the amount of water are the carbon content in the total raw material ( TC) is adjusted so that the cold crushing strength of the blast furnace carbon-containing unfired pellets is 50 kg / cm ² or more.

As the carbon content ratio (TC) in all raw materials increases, the cold crushing strength of the pellets decreases, so the amount of hydraulic binder added depends on the increase in the carbon content ratio (TC). As the amount increases, the amount of added water also increases, and by promoting the hydration reaction of the hydraulic binder, it is possible to maintain a cold crushing strength of 50 kg / cm ² or more.

In order to stably obtain the cold crushing strength of the blast furnace-containing non-fired pellets: 50 kg / cm ² or more, the hydraulic binder is preferably 5% by mass or more.

  At this time, in order to promote hardening by the hydration reaction of the hard binder and maintain the cold crushing strength of the pellets, the water content in all the raw materials needs to be 5 to 15% by mass. If the water content in the total raw material is less than 5% by mass, not only stable raw pellets can be produced, but also the hardening due to the hydration reaction of the hydraulic binder does not sufficiently occur, and the cold crushing strength after curing is low. Does not improve.

  On the other hand, if the amount of water in all the raw materials exceeds 15% by mass, the cold crushing strength of the pellets is reduced due to excess moisture. When the hydraulic binder exceeds 15% by mass, the dehydration reaction of the cement, which is an endothermic reaction in the blast furnace, reduces the rate of temperature rise at the shaft, resulting in a low-temperature reduction stagnation zone (low-temperature heat storage zone). The reduced pulverization in the blast furnace of the sintered ore that is generated and charged as the iron raw material for the blast furnace is promoted.

  Further, when the content of the hydraulic binder in the pellet exceeds 15% by mass, the ratio of iron and C in the pellet decreases, and the quality as a carbon-containing non-fired pellet for the blast furnace decreases. This increases the amount of slag generated in the furnace, which deteriorates the air permeability in the lower part of the furnace and makes stable blast furnace operation difficult.

  Further, when the hydraulic binder exceeds 15% by mass, the hydraulic binder is already dehydrated in the temperature range from the thermal preservation zone in the blast furnace to the reduction reaction equilibrium zone, and many voids are formed thereafter. In some cases, the effect of improving the hot strength by the network phase of metallic iron cannot be secured stably.

For the above reasons, the cold crushing strength of the carbon-containing unfired pellets for the blast furnace is stably obtained at 50 kg / cm ² or more, and the hot strength in the temperature range from the thermal preservation zone in the blast furnace to the reduction reaction equilibrium zone is obtained. In order to improve it stably, it is preferable to make a hydraulic binder into 5-15 mass%.

(Content of ultrafine particles having a particle size of 10 μm or less in the raw material containing fine powder iron)
As a result of the study by the present inventors, it was confirmed that iron ores of specific brands such as West Angelus and Denpogoa contain a large amount of ultrafine particles having a particle size of 10 μm or less. In addition, it was confirmed that the slurry cake after the lump ore was washed with water contained an extremely large amount of ultra fine powder covered with the lump ore.

  By adjusting the amount of one or more of these finely divided iron ores so that ultrafine particles having a particle size of 10 μm or less are contained in the iron ore in a ratio of 3.5% by mass or more with respect to the total raw materials, The crushing strength and hot strength between them can be kept high.

  Generally, in terms of mineralogy, weathered rocks or minerals having a particle size smaller than that of sand are called clay, and when wet, they are viscous and plastic. The definition of the particle size of this clay is not always clear, but it is 2 μm or less by the International Soil Society and the US Department of Agriculture, and 10 μm or less by the Japanese Agricultural Society (“Clay Handbook 2nd Edition” p3, Japan Clay Society (1994) ,reference).

  Also, the behavior of clay (ultrafine particles) in water varies depending on its chemical composition, its charge distribution and the type and amount of electrolyte ions dissolved in water, the pH of the aqueous solution, etc. In a uniformly dispersed state, when there is a lot of water, it becomes a slurry, and when the water content is low, it becomes a paste plastic. As the water content decreases, viscosity, viscoelasticity, and plasticity appear in sequence.

  Based on these mineralogical findings, the present inventors mainly utilized the above characteristics of ultrafine particles having a particle size of 10 μm or less contained in a large amount of a specific brand of iron ore. A study was conducted to increase the bonding force (adhesive force) between fine particles of 0.5 mm or less.

  As a result, ultrafine particles having a particle size of 10 μm or less, which are contained in a large amount in a specific brand of iron ore, exhibit the same characteristics as the above clay (ultrafine particles). It was confirmed that the viscosity, viscoelasticity, and plasticity of moisture existing between fine particles of 5 mm or less were expressed, and the binding force (adhesive force) was improved.

  In addition, by the action of these ultrafine particles having a particle size of 10 μm or less, the bonding strength (adhesion) between the raw material particles in the carbon-containing unfired pellets is improved, and the cold crushing strength and hot strength are improved. For this purpose, iron ore containing ultra-fine particles having a particle size of 10 μm or less in a ratio of 3.5% by mass or more with respect to the total raw materials needs to be blended as an iron-containing raw material.

  Therefore, in the present invention, in addition to the definition of the particle size of all the raw materials, the carbon content ratio (TC) in all the raw materials, and the median diameter of the fine powdery carbonaceous material, the fine powdery iron-containing raw material further It is preferable that iron ore is blended, and ultrafine particles having a particle size of 10 μm or less are contained in the iron ore in a proportion of 3.5% by mass or more based on the total amount of raw materials.

  When the content of ultrafine particles with a particle size of 10 μm or less in the iron ore to be blended is less than 3.5% in a ratio to the total raw materials, the ultrafine particles have a particle size of 0.5 mm or less during granulation. The effect of improving the cohesive strength (adhesive strength) by developing the viscosity, viscoelasticity, and plasticity of moisture existing between fine particles cannot be obtained sufficiently, and the raw pellet strength and cold crushing strength are further increased. The effect cannot be obtained.

  In addition, when the content of ultrafine particles having a particle size of 10 μm or less in iron ore is less than 3.5% by mass with respect to the total raw material, the temperature range from the thermal preservation zone of the blast furnace shaft portion to the reduction reaction equilibrium zone (900 to 1100 ° C.) The fine powder-derived metallic iron produced by the direct reduction reaction with the carbonaceous material in the pellet is uniformly dispersed in the pellet, and the effect of forming the network phase of metallic iron is sufficient. It can no longer be obtained.

  Therefore, in order to further improve the cold crushing strength and the hot strength, the content of ultrafine particles having a particle size of 10 μm or less in the iron ore blended in the finely divided iron-containing raw material is expressed as a ratio to the total raw material. 3.5 mass% or more is preferable.

  The effects of the present invention will be described below with reference to examples.

[Example 1]
Using the raw materials shown in Table 1, carbon-containing unfired pellets were produced. The raw material is a mixture ratio of cement (early strong Portland cement) of 10 to 14% by mass, carbonaceous materials (coke dust, fine coke, and blast furnace primary ash), and fine iron-containing raw materials (sintered dust and iron ore) The mixing ratio of (stone) was changed.

  After adding water and cement to these raw materials, they were kneaded with an Eirich mixer, granulated with a pan pelletizer to obtain raw pellets, and the raw pellets were then cured for two weeks. In addition, the water | moisture content of the raw pellet was adjusted to 10 to 14 weight% according to the cement amount to mix | blend.

  About the obtained carbon-containing non-baked pellet, raw pellet strength, cold crushing strength, crushing strength after reduction, and RAR when using 10% by mass of carbon-containing non-fired pellets were measured and evaluated.

  The raw pellet strength was expressed as the number of drops that resulted in destruction when dropped from a height of 1 m.

The crushing strength is measured in accordance with JIS M8718 by measuring the load value when one sample is broken by applying a compressive load at a specified pressure rate. Load value (kg / cm ² ).

The reduction of the carbon-containing non-fired pellets is performed using a reduction test apparatus that can simulate the reduction reaction in the blast furnace under a load. The reduction gas composition (CO is 36%, CO _{2 in} the thermal preservation zone and reduction reaction equilibrium zone of the blast furnace shaft portion). 14%, N ₂ 50%) and temperature: 1000 ° C.

  The ratio of reducing material during blast furnace operation is also used in the blast furnace by replacing the carbon-containing unfired pellets with 10% by mass of ordinary sintered ore using a test device (BIS furnace) that can simulate the reduction reaction in the blast furnace. The reducing material ratio (RAR) was evaluated.

  In addition, RAR of the conditions which do not mix | blend a non-baking pellet was 482 kg / tp. Moreover, the carbon-containing non-baked pellets were uniformly dispersed in the ore layer in the test apparatus (BIS furnace). The reducing material ratio (RAR) was calculated using a list diagram based on the result of steady state exhaust gas analysis.

  Table 2 shows the raw material blending conditions and the evaluation results of the carbon-containing non-fired pellets.

  As can be seen from Table 2, no. In Comparative Example 1, since the specified range of the total raw material particle size, the carbonaceous material carbon material particle size (median diameter) satisfies the range of the present invention, although the strength after reduction is sufficiently high, the carbon content ratio (TC) is Since it is lower than the range defined in the present invention, a large reduction in RAR was not obtained.

  No. In Comparative Example 2, the specified range of the total raw material particle size and the carbonaceous material particle size (median diameter) satisfy the range of the present invention, but the carbon content ratio (TC) is more than the range specified by the present invention. Since it is high, a large reduction effect of the reducing material ratio (RAR) is obtained, but the crushing strength after reduction is insufficient.

  No. In Comparative Example 3, the specified range of the total raw material particle size and the carbon content ratio (TC) satisfy the range of the present invention, and a large reduction effect of the reducing material ratio (RAR) was obtained. Since the particle size (median diameter) is excessively small, the crushing strength after reduction is low.

  No. In Comparative Example 4, the specified range of the total raw material particle size and the carbon content (TC) satisfy the range of the present invention, but the particle size (median diameter) of the carbonaceous material is excessively large. The crushing strength was low and the RAR reduction effect was small.

  No. In Comparative Example 5, the carbon content ratio (TC) and the particle size (median diameter) of the carbon material satisfy the scope of the present invention, but the carbon material contains a particle size of 2 mm or more, Since it falls outside the specified range of the raw material particle size, the crushing strength after reduction is low and the reducing material ratio (RAR) reduction effect is also small.

  On the other hand, no. 6 to 11 are inventions that satisfy the specified range of the total raw material particle size, the carbon content (TC), and the carbonaceous material particle size (median diameter) specified in the present invention, raw pellets, cold crushing strength, after reduction The crushing strength is good, and a large reducing material ratio (RAR) reduction effect is obtained.

  Among these invention examples, the content of ultrafine particles having a particle size of 10 μm or less in the blended iron ore is 3.5% by mass or more in terms of the ratio to the total raw materials. In Nos. 7 and 8, high excellent results were obtained for the raw pellet strength, the cold crushing strength, and the crushing strength after reduction.

[Example 2]
The above non-fired pellets were used and investigated as part of the raw material in a blast furnace having an effective volume of 5500 m ³ . Each level showed the average of operation results for about one month. From normal operation with a sintered ore ratio of 80%, a lump ore ratio of 15%, and a pellet ratio of 5%, It shifted to the operation which uses 3% of C = 22 mass% non-baking pellets.

  At that time, the sintered ore ratio, the lump ore ratio, and the pellet ratio were adjusted so as to minimize the effects of the amount of slag and moisture contained from the non-fired pellets. The carbon content of 10 kg / tp contained in the non-fired pellets reduced the mass coke ratio. As a result, the shaft efficiency was greatly improved, and the coke coke ratio could be further reduced.

  As a result of the above operation adjustment, the RAR could be significantly reduced from 480 kg / tp to 460 kg / tp.

It is a figure which shows the particle size distribution of various pulverized iron containing raw materials and pulverized carbonaceous materials. It is a figure which shows typically the process of the state change of each raw material particle | grains (iron oxide, carbonaceous material, cement (binder)) in a carbon-containing non-baking pellet in a cold and reduction temperature range. It is a figure which shows the relationship between the carbon material particle size (median diameter) and carbon content rate (TC) of the pulverized carbon material in a pellet, and the crushing strength after reduction. It is a figure which shows the relationship between the carbon material particle size (median diameter) and carbon content rate (TC) of the pulverized carbon material in a pellet, and the reducing material ratio (RAR) at the time of blast furnace operation. It is a figure which shows the relationship between the carbon content (TC) in a carbon-containing non-baking pellet, and the occupation rate in the height direction position of a sintered ore layer thickness.

Claims (6)

By adding a hydraulic binder to the finely divided iron-containing raw material containing 40% by mass or more of iron and a finely divided carbonaceous material containing 10% by mass or more of carbon, mixing and granulating while adjusting moisture, A method for producing a blast furnace carbon-containing unfired pellet having a cold crushing strength of 50 kg / cm ² or more, wherein the particle size of all raw materials is 2 mm or less, and the carbon content (TC) in all raw materials is 15 to 25 A method for producing a coal-containing non-fired pellet for a blast furnace, wherein the blending ratio of the pulverized carbon material is adjusted so as to be mass%, and the median diameter of the pulverized carbon material is 100 to 150 μm.   The method for producing a blast furnace carbon-containing non-fired pellet according to claim 1, wherein the hydraulic binder is granulated while adding 5 to 15% by mass and adjusting the water content to 5 to 15% by mass. .   The pulverized primary ash, coke dust, and powder coke are used as the pulverized carbonaceous material, or any one or more of them is used. Method.   The pulverized unburned pellets for blast furnace according to any one of claims 1 to 3, wherein one or two types of sintered dust and fine iron ore are used as the fine powder iron-containing raw material. Production method.   2. The fine powder iron ore is blended in the fine powder iron-containing raw material, and ultrafine particles having a particle size of 10 μm or less are contained in the iron ore in a proportion of 3.5% by mass or more with respect to the total raw material. The manufacturing method of the carbon-containing unbaking pellet for blast furnaces in any one of -4.   The blending ratio of the pulverized carbonaceous material is adjusted so that the carbon content ratio (TC) in the total raw material is 15 to 20% by mass. Method for producing carbon-containing unfired pellets for blast furnace.