JP2009030112A - Production method of blast furnace ore raw material - Google Patents

Abstract

The present invention proposes a method for producing a non-fired agglomerated ore, which is a raw material for blast furnace ore, using sintered powder and pre-furnace sieve powder.
A blast furnace ore which is a non-fired agglomerated ore by forming and agglomerating a sintered powder of 5 mm or less generated during the production of the sintered ore without forming it into a sintered ore. In the raw material method, as a raw material for molding, at least a binder and fine iron oxide are mixed in addition to the sintered powder, and then granulated, and then subjected to curing treatment in two stages of preliminary curing and steam curing. Manufactures ore raw materials for blast furnaces consisting of unfired agglomerated ores.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a blast furnace ore raw material, and particularly to a method for producing a blast furnace ore raw material using sintered powder generated during the production of sintered ore.

  In general, sintered ore used as a raw material for blast furnace ores in the iron making process is manufactured by adding secondary raw materials and carbonaceous materials to iron-containing raw materials such as iron ore powder and heating and firing them using a DL-type sintering machine. ing.

  For example, as shown in FIG. 1, a medium solvent such as quick lime and limestone and powdered coke are added to powdered iron ore, mixed with a mixer and then molded (granulated), and then placed on the pallet of the sintering machine. And then fired and fired, and then, through the crushing-cooling-sieving steps, a product sintered ore (fired agglomerated) having a particle size of about 5 to 50 mm is obtained. Supplying into the blast furnace. On the other hand, a sintered ore having a particle size of 5 mm or less, that is, a so-called sintered powder, is returned to the sintering machine as a return ore and fired again. In addition, the product sinter obtained by removing powder of 5 mm or less generated during the transfer process to the blast furnace with a sieve, so-called pre-furnace sieve powder, is also returned to the yard without being charged into the blast furnace. Then, it is refired (re-sintered) as part of the sintered raw material in the same manner as the return ore. That is, these return minerals and pre-furnace pre-sieving powders are once fired through a sintering process, and it is preferable in view of firing costs and transportation costs to recirculate them. It is not a treatment method.

  Thus, conventionally, agglomeration techniques have been proposed in which briquettes are made using sintered powder that has already been fired, and the briquettes can be directly charged into a blast furnace or the like. For example, Patent Document 1 discloses a method in which 20 to 25 mass% of water and cement are added to a sintered ore and kneaded and then granulated, and then subjected to a hydration curing treatment to form a briquette product. Yes.

Patent Documents 2 and 3 describe the production of non-fired agglomerated minerals that are granulated using a binder in order to use such sintered ore and pre-furnace sieving powder as raw materials for ores for blast furnaces. There is a disclosure about the method.
JP 58-123839 A JP 7-224329 A Japanese Patent Laid-Open No. 7-71824

  Among the above prior arts, the briquetting method described in Patent Document 1 uses Portland cement as a rapid setting agent in order to granulate sintered powder (-5 mm) which has deteriorated wettability and granulation property due to firing. This is a technology that uses a mixture of the slag and agglomerated as a raw material for a blast furnace. However, briquettes produced by this method, when viewed as a blast furnace charging material, crush strength at low and high temperatures, reduced powdering characteristics (JIS-RDI, hereinafter simply referred to as “RDI”), reducibility (JIS) -RI (hereinafter simply referred to as “RI”) was poor, and there was a need for improvement.

  Next, the methods described in Patent Documents 2 and 3 are all techniques for producing unfired agglomerated minerals, and are characterized in that they aim to improve cold strength by devising binders and carbonation curing treatment. However, the agglomerates obtained by these conventional techniques are also insufficient in reducing powdering properties (RDI) and reducing properties (RI), causing reduced powdering in a blast furnace, so There was a problem of causing a drop. Therefore, the agglomerates until now remain uneasy to use as a raw material for blast furnace ore directly without reusing the sinter powder for returning or pre-furnace sieving powder in a sintering machine.

An object of the present invention is to propose a method that can advantageously produce an unfired agglomerated mineral that is a raw material for blast furnace ore using sintered powder or pre-furnace sieve powder.
Another object of the present invention is to propose a technique capable of reliably producing a non-calcined agglomerate having high crushing strength at normal temperature and high temperature and good reduction powdering properties (RDI) and reducing properties (RI). There is to do.

  Inventors propose the manufacturing method of the blast furnace ore raw material which concerns on the following summary structure as a method effective in the implementation | achievement of the said objective, without the above-mentioned problem which the prior art has. That is, the present invention forms a non-fired agglomerated ore by forming and agglomerating a sintered powder of 5 mm or less generated during the production of the sintered ore without forming it into a sintered ore. In the method of making a raw material for blast furnace ore, the raw material for forming the non-fired agglomerated ore is composed of a material containing at least fine iron oxide in addition to the sintered powder, and further kneaded by adding a binder. A method for producing an ore raw material for a blast furnace, characterized in that it is molded and then subjected to curing treatment in two stages of precuring and steam curing to obtain a non-fired agglomerated ore.

  In the present invention, the molding raw material further includes pre-furnace sieving powder, the molding raw material further includes any one or more of dust, sludge, iron ore powder, and the binder 1 or more selected from cement, blast furnace granulated slag and binder, and the finely divided iron oxide contains a maximum particle size of 10 μm or less and contains 90 mass% or more of iron oxide. The resulting mill scale and refining dust, 3-6 mass% contained in the blended raw material, the cement being alumina cement or Portland cement, the binder being an organic binder and / or an inorganic binder The organic binder is selected from tar, pitch, molasses and synthetic resin binder The synthetic resin binder is a phenol resin binder, or the pre-curing is a treatment that is left on the yard for 30 minutes to 5 hours at a temperature of 40 ° C. or lower, The steam curing is a treatment exposed to water vapor at a temperature of 70 to 90 ° C. for about 15 to 48 hours, and the curing treatment is a hydration curing treatment or a carbonation curing treatment with the hydration curing treatment. The non-calcined agglomerated mineral being treated, the uncalcined agglomerated mineral having an RI (reducibility) of 65% or more, and the uncalcined agglomerated mineral being RDI ( A reduction powder) of 30% or less provides a more effective solution.

According to the present invention according to the above-described configuration, the sintered ore and the pre-furnace sieve powder that were originally recirculated and refired are immediately agglomerated without being recirculated. Since it can be used directly as an input material, it is possible to achieve a reduction in sintering costs, various basic units, sintering equipment costs, and maintenance costs. In addition, according to the proposed technology, the reduction of the sintered coagulant brings about a ripple effect such as effective use of resources and contribution to environmental protection (CO ₂ reduction).

  Moreover, according to the present invention, in addition to being excellent in compression moldability, non-fired agglomerated minerals with high crushing strength and cold strength (DI) are produced using sintered powder for return ore, pre-furnace sieve powder, etc. as raw materials. can do. Moreover, even when the obtained unfired agglomerated ore is charged into the furnace as a raw material for blast furnace ore, it has excellent reduced powdering characteristics (RDI) and reducibility (RI) at low and high temperatures. This will stabilize the operation of the blast furnace and reduce the cost of pig iron production.

The sintered ore (product) is usually crushed at the pallet end after firing, and the particle size is adjusted to a size of 5 to 50 mm with a vibrating sieve or the like. At this time, the sintered powder (particle size: -5 mm) classified under the sieve of the vibrating sieve is generally returned to the sintering machine, and is again subjected to sintering treatment together with new iron ore powder as return ore. Is normal. In order to recycle the sintered powder as a return ore, as described above, it is necessary to review such usage from the viewpoints of an increase in manufacturing cost, transportation cost, and environmental protection (CO ₂ reduction). That is, the difference between return ore (sintered powder) and product sintered ore is simply that the particle size is different. Therefore, if the sintered powder that becomes the sintered ore is formed into the same particle size (> 5 mm) as the product (sintered ore), it should be able to be used as a raw material for ore for blast furnace.

  Under the above-mentioned concept, the present invention re-sinters the -5 mm sintered powder, which becomes a sintered ore, into a size of about 5 to 50 mm, thereby re-sintering it. This is a method of making agglomerates into raw materials that are effective as raw materials for blast furnace ores.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a flow diagram of a process for producing a raw material for blast furnace ore made of unfired agglomerated ore. The example described below is an example of manufacturing briquettes by a molding machine, but it is a matter of course that the same effect can be obtained even when pellets are manufactured using a granulator instead of the molding machine.

  In the present invention, the raw materials for molding to be non-fired agglomerated materials such as sintered powder, pre-furnace pre-sieving powder, and fine powdered iron oxide as main starting materials are stored in compounding tanks 1, 2, and 3, respectively. Then, it is cut out on the conveyor 5 by the quantitative cutting device 4 so as to have a predetermined blending ratio. Next, these forming raw materials are mixed in the first mixer 6 and, if necessary, the second mixer 7. If necessary in this mixing step, humidity adjustment (moisture addition) may be performed.

  Thereafter, the mixed raw material is sent to the raw material tank 8. The raw material tank 8 stores cement, blast furnace granulated slag, organic binder, inorganic binder, and the like. These binders are mixed with the mixed raw material in a mixer 9 (usually using a hug mill), and humidity is adjusted and kneaded as necessary. Next, the mixed raw material is supplied to the molding machine 11 through the kneader 10 and agglomerated into a predetermined size. The agglomerated ore obtained is discharged through the shaking sieve 12 and carried directly to the blast furnace or on the yard.

  In the production process of the non-fired agglomerated mineral produced as described above, the first feature of the present invention is the kind and blending of the forming raw material that is the starting raw material. That is, the raw materials for molding used in the present invention are mainly generated in a sintered powder having a size of 5 mm or less, which is supposed to be sintered ore, and sieving powder before the blast furnace (in the conveying process toward the blast furnace). 5 mm or less under-sieving powder, in particular powder generated in front of sintered ore furnace). In the present invention, as described later, at least fine iron oxide, for example, hematite powder, Rusner iron oxide powder, etc. is added to these molding raw materials, and the cement plays a role as an inorganic binder, an organic binder, and an auxiliary binder. For example, a binder made of alumina cement, Portland cement or granulated blast furnace slag is added, and then these are put into a mixer (mixer) and kneaded, and then put into a molding machine or a granulator (molding) ) The particle size distribution and chemical composition of typical sintered powder and pre-furnace sieving powder as molding raw materials are shown below.

  The second feature of the present invention is the selection of the binder. In the present invention, the sintered powder mainly used as a forming raw material is fired compared to an iron ore raw material or the like, and therefore has poor wettability. For example, a blast furnace iron ore raw material (mount Newman or lobe) In the case of River, Sendy), the contact angle with water is 37.0-48.3 deg, whereas the sintered powder is as high as 74.1 deg. Is essential. In this case, as the binder, a hydraulic binder such as alumina cement, Portland cement or blast furnace granulated slag, and other inorganic binders (bentonite, water glass) are used.

  Such hydraulic binder is not particularly limited as long as it can exhibit a sufficient strength in the cold due to the hydration effect, and for example, one or more of the above cement and granulated blast furnace slag can be used. .

  However, if a hydraulic binder such as cement is used, the crushing strength at room temperature can be increased, and the transfer from the production site to the blast furnace becomes easy. In addition, it helps to maintain its shape in the low temperature area in the upper part of the blast furnace, but in the high to low sound area in the middle and lower parts of the blast furnace, the strength decreases due to thermal decomposition of cement hydrate, It is known that it causes pulverization in the lower part to the lower part and the resulting deterioration in air permeability.

  For such a problem, an adhesive hydrocarbon mixture such as tar or pitch may be mixed as a binder. However, the non-calcined agglomerate formed using such a binder evaporates at 200 ° C. and produces gaseous carbon at a high temperature to improve the high temperature strength, but in the low temperature region at the top of the blast furnace. The problem is that the crushing strength is poor.

  Therefore, in the present invention, in order to overcome the problems of the binders such as cement and pitch described above, one or more selected from organic binders such as molasses, tar, pitch or synthetic resin binders are used. It was to be. In the present invention, it is preferable to use a phenol resin, especially the synthetic resin binder.

  The phenol resin which is the synthetic resin binder is characterized in that it functions as a binder at normal temperature and carbon generated by carbonization in a high temperature region in the blast furnace functions as a binder. In addition, the phenol resin which exists as a binder in the non-baking agglomerated mineral of the present invention is a resin obtained by thermosetting a phenol resin precursor.

  By using the above-mentioned phenol resin, which is a synthetic resin binder, as a binder for forming raw materials such as sintered powder and pre-sieving powder, non-fired agglomerated ore is hardened phenol at room temperature at the time of molding. Crushing strength of 390N / piece can be secured by the binder function of the resin itself and the moldability is improved. At the time of use, carbon generated by carbonization of the phenolic resin in the high temperature range of the blast furnace exhibits the binder function, so at least 1000 ° C. The crushing strength of 100 N / piece or more can be secured in the temperature range up to. Therefore, it can be said that the non-calcined agglomerate formed using such a binder is less pulverized in the yard, in front of the blast furnace and in the furnace, and exhibits excellent characteristics as a blast furnace ore raw material.

  In particular, the phenol resin that enters the blast furnace as a part of the component of the non-fired agglomerated mineral is decomposed by heat and partly gasified, and carbon (thermal decomposition residue) is generated in the non-fired agglomerated mineral. That is, the phenol resin has a ratio of carbon remaining when heated to 500 ° C. or higher in a non-oxidizing atmosphere (residual carbon ratio) of about 40% by mass or more compared to almost 0% of many resins such as acrylic and polyolefin. A high point is a characteristic binder. Therefore, the non-fired agglomerated agglomerates obtained by agglomerating phenol resin as a binder retain the crushing strength by the binder function of the phenol resin itself from the time of charging the blast furnace to about 350 ° C., and between 350 ° C. and 500 ° C. In order to develop the hot crushing strength of the unfired agglomerated minerals, the carbon produced by carbonization of the phenolic resin functions as a binder in the high temperature range. Become.

  By the way, in the present invention, an organic binder and an inorganic binder are added to the raw material for molding consisting of the above sintered powder and the pre-furnace sieve powder, but the product is simply formed by adding these binders. A shape alone cannot provide the strength required for normal handling and transport processes. That is, when the non-calcined agglomerate as in the present invention is used by directly sending it to the blast furnace, the product is pulverized due to impact at the chute part or blast furnace charging part having a large drop, resulting in a decrease in yield. . Therefore, in the present invention, a device for increasing the impact strength of the formed product after molding, that is, the addition of such a material was considered.

Under such a concept, attention was paid to fine iron oxide as what is considered to be effective in developing the impact strength. In the present invention, in addition to the sintered powder and the pre-furnace pre-sieving powder, fine iron oxide is further blended as a forming raw material. As the fine powdered iron oxide, fine powder which is composed essentially of iron oxide and contains 90 mass% or more of fine granular iron oxide having a particle size of 10 μm or less is suitable for improving the strength. However, a very small amount of substances other than iron oxide (for example, SiO ₂ , Al ₂ O _3, etc.) may be included as part of the particles together with iron oxide, or included as particles not containing iron oxide. It may be a small amount (≦ 1 mass%). The reason is to reduce the influence on the slag ratio and slag component design when the fine iron oxide is charged into the blast furnace. The iron oxide may be any of Fe ₂ O ₃ (hematite), Fe ₃ O ₄ (magnetite), and FeO (wustite).

Examples of such finely powdered iron oxide include steel pickling line recovered powder (so-called “Rusner iron oxide powder”, etc.), mill cases and refined dust generated in the steel manufacturing process, and one or more of these may be used. it can. Here, Rusner iron oxide powder refers to the pickling sludge generated when the surface iron oxide layer is removed by pickling (pickling with hydrochloric acid solution) before rolling in a steel material manufacturing process such as a steel plate. It was obtained by processing by a method such as firing, and Fe ₂ O 3: 99.4 to 99.9 mass%, CaO ≦ 0.02 mass%, SiO ₂ ≦ 0.004 mass%, Al ₂ O ₃ ≦ 0. 01 mass%, MgO ≦ 0.002 mass%, etc. It is a high purity and fine powder iron oxide having a particle size of 10 μm or less.

In addition, in the present invention, another reason for blending the fine iron oxide is to develop high temperature strength. That is, according to the inventors conducting a heat treatment test on the granulated product after molding in an N ₂ atmosphere, in the case of the agglomerate containing about 3 to 6 mass% of the Lusner iron oxide powder, the granulated product is about 200 ° C. to 1000 ° C. When the temperature was raised to ℃, the strength index was 78% at the temperature of 1000 ℃, whereas the strength index of the compound without the Rusner iron oxide powder was 58%, which is due to the solid-phase sintering action of the iron oxide powder. It was considered that high temperature strength was developed. If this iron oxide powder is less than 3 mass%, the effect of improving the strength is weak, whereas if it exceeds 6 mass%, the effect is saturated.

  Further, in the production of the non-fired agglomerated ore of the present invention, as described above, the forming raw material and binder composed of sintered powder, fine iron oxide and the like are the main constituent components, but other components as necessary. For example, one or more of iron ore powder, various dispersants, hardening accelerators, limestone fine powder, fly ash, silica fine powder and the like can be blended in an appropriate amount as long as the effects of the present invention are not impaired. However, about reducing materials, such as coke powder, you may mix | blend about 20 mass% separately according to the use purpose separately.

  The particle size of the unfired agglomerated mineral produced by the application of the method of the present invention (spherical equivalent particle size in a normal temperature atmosphere) is preferably more than 5 mm to less than 50 mm, preferably about 8 to 30 mm. If the particle size of the unfired agglomerated mineral is 5 mm or less, the air permeability of the raw material packed layer when charged in the blast furnace may be deteriorated, while if the particle size is 50 mm or more, the reducibility may be reduced. It becomes more prominent when the size is 8-30 mm.

  When the non-fired agglomerated mineral is produced based on the method of the present invention, first, water, a binder, or other materials are added to the mixed raw material composed of the molding raw material and the like, and then stirred (kneaded), and then molded (manufactured). To obtain a molded body (granulated product). The granulated product is then humidified as necessary and cured to obtain the desired unfired agglomerated mineral.

  As a molding method, any of a compression granulation method using a briquette molding machine and a rolling granulation method using a disk pelletizer or a drum type granulator may be used. The briquetting machine mechanically compresses the particle group, so the filling rate of the molded product increases and the green strength (the strength immediately after molding tends to increase, but the cold strength after curing is the quality and quantity of the binder) There is no significant difference between the rolling granulation method and the compression granulation method.In general, the compression granulation method has a uniform particle size and properties compared to the rolling granulation method. While it is easy to make things, it is characterized by high equipment and repair costs.

  In the present invention, the third feature is the curing treatment of the granulated product. In general, in the case of the present invention, the granulated material is made of a hydraulic binder such as cement in order to bind the forming raw material made of sintered powder, pre-furnace sieve powder and the like into pseudo particles. I came. Such a binder is a strength of agglomerated ore by increasing the bonding strength between raw material powders for molding when mainly curing agglomerated ore after molding in the presence of moisture. Demonstrate the effect of expressing

The green agglomerated ore after the molding is mainly cured by a method such as depositing it in a yard, and a process of expressing strength is performed using a hydration reaction that occurs at this time. In this curing treatment, in addition to the hydration reaction between CaO and moisture in the binder (CaO + H ₂ O → Ca (OH) ₂ ), CaO in the binder is eluted into moisture to become Ca (OH). It is effective to develop the strength of the green agglomerated mineral by a carbonation reaction in which it reacts with CO ₂ in the atmosphere to produce CaCO ₃ . However, when normal curing such as yard accumulation is performed, it takes a long time (48 hours or more) to develop the required strength, and a large yard space must be secured. Then, the carbonation reaction hardly occurs. Of course, in order to eliminate the drawbacks of using such a hydraulic binder, the use of organic binders such as tar, pitch, and molasses is effective, and the curing time can be shortened.

  In the method for producing a non-fired agglomerated ore according to the present invention, one or two types of sintered powder or pre-furnace sieving powder (blast furnace product) and the above-mentioned fine powder oxidation having a relatively smaller particle size than these raw materials. When adding 1-6 mass% molasses or a diluent containing the above-mentioned amount of synthetic resin binder (phenolic resin) as a binder to the mixed powder with iron, kneading and agglomerating to 3 mm or more with a molding machine In addition, the mixed raw material mixed and conditioned is first preliminarily left at room temperature (40 ° C. or lower) with a predetermined curing time (2 hours or longer, preferably 4 hours or longer) and 15 to 70 to 90 °. Exposure to steam for about 48 hours, followed by steam curing. FIG. 2 is a schematic diagram illustrating a curing pattern employed in the present invention.

  And in this invention, the steam curing mentioned above which exposes a molded object in water vapor | steam atmosphere is performed following the said preliminary curing. By performing this steam curing, the caking action of the inorganic binder and the organic binder is not impaired, and the strength of the raw granulated material is improved and a non-fired agglomerated mineral having a good yield can be obtained. It becomes like this. The unfired agglomerated ore obtained by performing such steam curing treatment exhibits a crushing strength (for example, 100 N / piece or more) that can sufficiently withstand handling during transportation. This is also apparent from the graph shown as FIG.

  As a method of steam curing, in addition to a method using a curing tower or a steam blowing device, a cover is put on the granulated material on the yard after the preliminary curing, and steam is blown under the cover. Even if the simple method is implemented, the same effect can be obtained. In this steam curing treatment, the reason why the temperature in the atmosphere is set to 70 to 90 ° C. is for efficiently expressing the hydration reaction. If the time is set to 15 to 48 hours, it is less than 15 hours. In this case, the hydration reaction does not proceed sufficiently and the strength does not increase. The reason why the hydration reaction is 48 hours is that the hydration reaction is almost completed at this time, and further curing is inefficient.

  In the present invention, as a desirable curing treatment, it has been found that the following curing treatment over two stages is effective instead of conventional steam curing and carbonation curing. That is, in the present invention, when the agglomerated material is agglomerated to a size of more than 5 mm with a molding machine, first, a predetermined curing time (30 minutes to 5 hours) is obtained at room temperature (40 ° C. or lower). It was decided to perform steam curing by exposing to steam for 15 to 48 hours at 70 to 90 ° after this preliminary curing. FIG. 2 is a diagram of a curing pattern employed in the present invention.

It should be noted that in the above two-stage curing, the pre-curing time performed at a room temperature of 40 ° C. or lower is at least 30 minutes or more, preferably 2 hours or more and 5 hours or less. This is because if the pre-curing is out of these times, the crushing strength of the granulated material will decrease or the effect will be saturated. Here, after mixing and conditioning, the mixed raw material is not immediately molded by a molding machine, but is preliminarily cured at room temperature. The reason why the pre-cured CaO (free lime) is contained in the sintered raw material or the raw material This is because a hydration reaction is caused with moisture added at the time of humidity control to convert it into Ca (OH) _{2 and the} like, and this reacts slowly with other binders, thereby effectively acting to suppress a rapid reaction. This is also clear from the relationship (for each curing temperature) between the precuring time and the crushing strength shown in FIG.

  And what is characteristic in this invention is performing the steam curing mentioned above which exposes a molded object (non-baking agglomerated mineral) in water vapor | steam atmosphere following the said preliminary curing. By performing this steam curing, the caking action of the inorganic binder is not harmed, the strength of the molded product (non-fired agglomerated mineral) is improved, and a non-fired agglomerated mineral having a good yield is obtained. Will be able to. The unfired agglomerated ore obtained by performing such steam curing treatment exhibits a crushing strength (for example, 100 N / piece or more) that can sufficiently withstand handling during transportation. This is also apparent from the graph shown as FIG.

  As a method of steam curing, in addition to a method using a curing tower or a steam blowing device, a cover is put on the granulated material on the yard after the preliminary curing, and steam is blown under the cover. Even if the simple method is implemented, the same effect can be obtained. In this steam curing treatment, the reason why the temperature in the atmosphere is set to 70 to 90 ° C. is for efficiently expressing the hydration reaction. If the time is set to 15 to 48 hours, it is less than 15 hours. In this case, the hydration reaction does not proceed sufficiently and the strength does not increase. The reason why the hydration reaction is 48 hours is that the hydration reaction is almost completed at this time, and further curing is inefficient.

  In addition, in the curing treatment over the two stages described above, particularly in the latter half steam curing, carbon gas may be blown together with high-temperature steam to perform so-called carbonation treatment. This method is not limited to the case where a hydraulic binder such as cement is included as a binder, but the dissolution rate of a solvent such as calcium ferrite contained in the granulated material, particularly in the sintered powder or in the pre-sieving powder before the furnace. This is because the hardening reaction is promoted by carbonation and the impact strength of the unfired agglomerated mineral can be increased in a short time.

  In the present invention, drying may be performed after curing. In this regard, in the conventional production of non-calcined agglomerated minerals, drying after curing is not carried out, and the non-calcined agglomerated minerals obtained after curing are directly charged into the blast furnace as blast furnace ore raw materials. On the other hand, in the present invention, if necessary, the unfired agglomerated mineral is dried at a temperature of about 80 to 150 ° C. with a drying apparatus or the like after curing the blast furnace and put into the blast furnace. In addition to improving the impact resistance strength of the blast furnace, the content of free moisture in the unfired agglomerated ore is reduced to 4 mass% or less, preferably 2 mass% or less to maintain air permeability in the blast furnace.

  In other words, explosion (pulverization) of unfired agglomerated ore in the blast furnace is caused by evaporation of free moisture in the unfired agglomerated ore into the blast furnace, and the vapor pressure is reduced to the internal pressure. As a result, the unfired agglomerated swell expands and cracks occur, and eventually explodes and pulverizes, deteriorating the air permeability in the furnace.

  In particular, when unfired agglomerated ore is charged into a blast furnace, the explosion ratio of the unfired agglomerated ore increases when the furnace temperature rises or the free water content in the unfired agglomerate increases. However, the explosion (pulverization) ratio (%) decreases with a decrease in temperature and a decrease in free water content.

  By the way, the unfired agglomerated mineral produced through the above-described production process suitable for the present invention has particularly high high temperature crushing strength. That is, the load softening test conducted by the inventors (after reduction at 550 ° C., 700 ° C. and 900 ° C., after cooling, the reduction rate was calculated from the weight change of individual particles (12 samples), and the crushing strength was determined by autograph. The results are shown in FIGS. 5 to 7 in comparison with the sintered ore, but both were higher than the target crushing strength and there was no difference from the sintered ore.

  Moreover, the non-calcined agglomerated mineral produced by the method suitable for the method of the present invention has a reduced powdering characteristic (RDI) of less than 30% and a reducibility (RI) of higher than 65%. According to the experiments conducted by the inventors, as shown in FIG. 8, results of RDI of 20% or less and RI of 73% or more were obtained. Sintered ores, calcined pellets, ores measured under the same conditions Compared to the above, it has been clearly shown that it exhibits excellent properties as a blast furnace ore raw material.

In the above experiment, a 500 g sample was used, and this was reduced at 900 ° C. for 3 hours in an atmosphere of (a) RI test: CO 30 vol%, N ₂ 30 vol%.
(B) RDI test: Reduced at 550 ° C. for 0.5 hours in an atmosphere of CO 30 vol% and N ₂ 30 vol%, and shows the result for the ratio of drum test → 2.8 mm.
And since the structure observation of the non-fired agglomerated mineral and sintered ore obtained in this experiment was performed, the cross-sectional structure photograph is shown in FIG. 9, but the non-fired manufactured by the method suitable for the method of the present invention In the case of agglomerated minerals, cracks occurred in the sintered powder, but the cracks did not propagate in the matrix, while cracks propagated throughout the sintered ore.

As a raw material for molding, the sintered powder for return ore and the pre-furnace sieve powder (shown in Tables 1 to 4), as a binder, any one or more of molasses, phenol resin, alumina cement, as fine iron oxide The mixed raw material to which Rusner iron oxide powder was added was shaped according to a production flow as shown in FIG. 1 and subjected to a predetermined curing treatment to produce a non-fired agglomerated ore. Here, as the Rusner iron oxide powder, the steel material pickling line collection powder described in paragraph (0033) was used.
Table 5 shows the chemical composition of the molding raw materials and other blended raw materials used. The components of the sintered powder and the pre-furnace sieve powder are the same, but the sintered powder has a slightly fine particle size and an average particle size of 1.49 mm. On the other hand, the pre-furnace sieving powder has a slightly coarse particle size and an average particle size of 2.52 mm. As the Rusner iron oxide powder, one having an extremely high iron oxide content (≧ 99.4 mass%) and fine particles (the ratio of the particle size of 10 μm or less is 90 mass% or more) was used.

The unfired agglomerated ore of each example was charged into the blast furnace together with the iron ore raw material, and the changes in the cold strength and blast furnace operating status of the unfired agglomerated ore were investigated. The results are shown in Table 6 together with the blending particle size distribution of the sintering raw material and the binder blending amount. The blending ratio of the raw materials charged into the blast furnace was set as follows: uncalcined agglomerated mineral: 12 mass%, sintered ore: 79 mass%, lump ore: 9 mass%.
About the cold intensity | strength of a non-baking agglomerated ore, the powder rate in a yard and the powder rate in a blast furnace top were measured, and the difference (powdering rate at the time of transport) evaluated. If the agglomerate has a particle size of 5 mm or more, it can be used as a raw material for a blast furnace, so particles of −5 mm (= particle size of 5 mm or less) are defined as powder, and the mass ratio is set to a powder rate of −5 mm. .

  Also, the “blow-out phenomenon” of the number of blow-throughs shown in Table 6 means that the flow of reducing gas is stopped by increasing the pressure loss in the blast furnace, the pressure in the furnace rises, and reaches a certain pressure. When this happens, it means a phenomenon in which the rising of the reducing gas explosively resumes. In this case, since the charge in the furnace moves with the gas simultaneously with the resumption of the gas flow, the distribution of the charge deposited in layers is disturbed. If the distribution of the charge is disturbed, the air permeability is further deteriorated, and problems such as poor reduction of iron oxide are caused. There is also concern about thermal adverse effects on various facilities due to mechanical damage to the furnace body due to the rise and rapid hot gas ejection.

Invention Example 1 is an example containing 3 mass% of fine iron oxide and containing an organic binder.
Invention Example 2 is an example containing 6 mass% of fine iron oxide, and the binder is an example in which alumina cement and an organic binder are mixed.
Invention Example 3 is an example containing 5 mass% of fine iron oxide, and the binder is an example in which only an organic binder is blended.
Comparative Example 1 is an example containing no organic binder and fine iron oxide.
The comparative example 2 is an example which does not give precuring.
Comparative Example 3 is an example in which the steam curing time is short.
Comparative Example 4 is an example in which no organic binder is blended and curing is not performed.

  As can be seen from the operation results shown in Table 6, in the example in which the non-calcined agglomerate suitable for the example of the present invention was charged, the non-calcined agglomerated mineral in the comparative example is being transported to the blast furnace. It turns out that there is little powdering of. In addition, when looking at the operation of the blast furnace, the amount of dredging is large, the ratio of reducing material is low, and there is no blow-through phenomenon. From these results, it is understood that blast furnace operation can be remarkably improved when the unfired agglomerated mineral produced by the method of the present invention is used.

  Although this invention is description regarding the manufacturing method of the non-baking agglomerated mineral using the sintered powder for return ore as a blast furnace ore raw material, it is applicable also to iron-making raw material manufacturing techniques, such as a fired agglomerated mineral.

It is a diagram which shows the manufacture flow of the ore raw material for blast furnaces which consists of a non-baking agglomerated mineral. It is a diagram of a curing treatment pattern suitable for the present invention. It is a graph which shows the influence which a precuring process has on crushing strength. It is a graph which shows the influence which steam curing treatment has on crushing strength. It is a graph which shows the relationship between the reduction rate in 550 degreeC, and crushing intensity | strength of the unbaking agglomerated mineral manufactured by applying this invention method. It is a graph which shows the relationship between the reduction rate in 700 degreeC and the crushing strength of the unbaking agglomerated mineral manufactured by applying this invention method. It is a graph which shows the relationship between the reduction rate in 900 degreeC, and crushing intensity | strength of the unbaking agglomerated mineral manufactured by applying this invention method. It is a graph which shows the relationship between the reducibility and the reduction | restoration powdering characteristic about the unbaking agglomerated mineral manufactured by applying this invention method. It is a cross-sectional structure | tissue photograph about the non-baking agglomerated mineral manufactured by applying the method of this invention.

Explanation of symbols

1-3 Mixing tank 4 Fixed amount cutting device 5 Conveyor 6 1st mixer 7 2nd mixer 8 Raw material tank 9 Mixer 10 Kneader 11 Molding machine 12 Shaking sieve

Claims (15)

Sintered powder of 5 mm or less generated during the production of sintered ore is shaped and agglomerated without forming sintered sinter, thereby forming a non-fired agglomerated ore, which is used as a blast furnace ore raw material. In the method
As a forming raw material for making the unfired agglomerated mineral, it is composed of a material containing at least fine iron oxide in addition to the sintered powder, and further molded by adding a binder and then pre-cured and A method for producing an ore raw material for a blast furnace, which is subjected to curing treatment in two stages with steam curing to form an unfired agglomerated ore. The method for producing an ore raw material for a blast furnace according to claim 1, wherein the raw material for molding further includes pre-furnace presieving powder. The method for producing a blast furnace ore material according to claim 1 or 2, wherein the molding material further contains at least one of dust, sludge, iron ore powder and the like. The finely divided iron oxide is Rusner iron oxide powder having a maximum particle size of 10 μm or less and containing 90 mass% or more of iron oxide, mill scale generated in the steel manufacturing process, refining dust, and 3 to 6 mass% contained in the blended raw material The method for producing an ore raw material for a blast furnace according to claim 1, wherein: The method for producing an ore raw material for a blast furnace according to claim 1, wherein the binder is at least one selected from cement, blast furnace granulated slag, and a binder. The said cement is an alumina cement or a Portland cement, The manufacturing method of the blast furnace ore raw material of Claim 5 characterized by the above-mentioned. The method for producing an ore raw material for a blast furnace according to claim 5, wherein the binder is an organic binder and / or an inorganic binder. The method for producing an ore raw material for a blast furnace according to claim 7, wherein the organic binder is at least one selected from tar, pitch molasses, and a synthetic resin binder. The method for producing an ore raw material for blast furnace according to claim 8, wherein the synthetic resin binder is a phenol resin binder. The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 9, wherein the pre-curing is a treatment that is allowed to stand on a yard at a temperature of 40 ° C or lower for 30 minutes to 5 hours. . The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 9, wherein the steam curing is a treatment of exposing to water vapor at a temperature of 70 to 90 ° C for about 15 to 48 hours. . The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 3, wherein the curing treatment is a hydration curing treatment or a treatment for performing a carbonic acid curing treatment together with a hydration curing treatment. . The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 12, wherein the cured non-fired agglomerated mineral is dried. The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 13, wherein the unfired agglomerated ore has an RI (reducibility) of 65% or more. The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 14, wherein the unfired agglomerated ore has an RDI (reduction powdering characteristic) of 30% or less.

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