JP2009030113A - Method for producing ore raw material for blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing non-fired agglomerated ore as an ore raw material for a blast furnace using sintered powder or straight undersized powder. <P>SOLUTION: In the method where sintered powder of ≤5 mm generated upon the production of sintered ore is formed without being made into sintering return ore, so as to be agglomerated, thus an ore raw material for a blast furnace as non-fired agglomerated ore is produced, as the raw material for forming, other than the above sintered powder, at least a binder including an organic binder is mixed, the mixture is thereafter formed, and is subsequently subjected to two stage curing treatment of preliminary curing and steam curing, so as to produce the ore raw material for a blast furnace composed of non-fired agglomerated ore. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an ore raw material for blast furnace, and in particular, a method for producing an ore raw material for blast furnace directly from the sintered powder without converting the −5 mm sintered powder generated during the production of the sintered ore. Propose about.

  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 passed through crushing-cooling-sieving steps to obtain a sintered product ore (fired agglomerate) having a particle size of about 5 to 50 mm, which was used as a blast furnace Supplying in. On the other hand, a sintered ore having a particle diameter 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 recycling them is economical in terms of firing costs and transportation costs. It cannot be said to be a typical 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 have CaO and SiO ₂ as the main components when viewed as blast furnace charging raw materials, so that an extra slag forming component is provided, so that the non-fertility of the raw materials is deteriorated. In addition, the crushing strength, reduced powdering characteristics (JIS-RDI, hereinafter simply referred to as “RDI”), and reducibility (JIS-RI, hereinafter simply referred to as “RI”) at low and high temperatures are deteriorated and improved. There was a need.

  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 be used directly as raw materials for blast furnace ores without reusing the sintered powder for return or sieving before the furnace with a sintering machine. It was.

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 provide a technology that can reliably produce a non-fired agglomerated ore that has high crushing strength at room temperature and high temperature and that has good reduced powdering properties (RDI) and reducibility (RI). It is to propose.

  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 blast furnace ore raw material, as the raw material for forming the non-fired agglomerated ore, the sintered powder is included, and the sintered powder is added with a binder containing at least an organic binder and then kneaded. And then, it is a method for producing an ore raw material for a blast furnace, characterized in that it is subjected to curing treatment in two stages of preliminary curing and steam curing to form a non-fired agglomerated ore.

  In the present invention, the molding raw material further includes a pre-furnace sieve powder, the molding raw material further includes any one or more of dust, sludge, iron ore powder, In addition to an organic binder, it contains a cement and / or an inorganic binder, the cement is alumina cement or Portland cement, and the inorganic binder is at least one of blast furnace granulated slag, bentonite and water glass. The organic binder is molasses or a synthetic resin binder having a function as a binder even after water has evaporated, the synthetic resin binder is a phenol resin binder, and the pre-curing is 40 It is a treatment to be left on the yard for 30 minutes to 5 hours at a temperature of ℃ or less, the steam curing is 70 to 90 ℃ 15 to 48 hours at a time, and the curing treatment is a hydration curing treatment or a treatment of performing carbonation curing treatment together with the hydration curing treatment, after the curing treatment. Performing drying, the non-calcined agglomerate has an RI (reducing property) of 65% or more, and the non-calcined agglomerated material has an RDI (reducible powdering property) of 30% or less. Provides a more effective solution.

According to the present invention related to the above-described configuration, the sintered ore and the pre-furnace sieve powder that were originally subjected to circulation reprocessing and re-baking are immediately agglomerated without recirculation, and this is charged into the blast furnace. Since it can be used directly as a raw material, it is possible to achieve a reduction in sintering cost, various basic units, sintering equipment cost, and maintenance cost. Moreover, this proposed technique brings about ripple effects 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.

  In addition, the non-calcined agglomerated mineral produced under the method of the present invention can maintain a crushing strength of 390 N / piece or more due to the binder function of the cured phenol resin itself at room temperature, and the phenol resin at a high temperature range in the furnace. Since carbon produced by carbonization exhibits a binder function, it is possible to maintain a crushing strength of 100 N / piece or more in a temperature range up to at least 1000 ° C. Therefore, there is little pulverization in a blast furnace and a yard, and it has excellent performance as an unfired agglomerated ore.

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) generated under the vibrating screen is generally returned to the sintering machine, and returned to the sintering process together with new iron ore powder. It is normal. As described above, recirculation of the sintered powder as return ore is disadvantageous from the viewpoints of an increase in manufacturing cost and transportation cost and environmental protection (CO ₂ reduction), and a review is required. That is, the difference between the return ore (sintered powder) and the product sintered ore is merely that the particle size is different. Therefore, if the sintered powder that becomes the sintered ore is reshaped to the same particle size (> 5 mm) as the product (sintered ore), it should be used as it is as a raw material for blast furnace ore.

  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 effective as raw materials for blast furnace ore without any changes.

  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. In this raw material tank 8, in addition to an inorganic binder such as blast furnace granulated slag, a binder such as an organic binder and cement is also stored. 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 is then discharged through the shaking screen 12 and carried directly to the blast furnace or on the yard.

  Among the processes for producing the unfired agglomerated ore produced as described above, the first feature of the present invention is the type 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 sintered powder having a size of 5 mm or less, which should originally be sintered ore, and sieving powder before the furnace (5 mm generated in the conveying process toward the blast furnace). The following sieving powder, in particular, pre-furnace sieving powder of sintered ore). For these raw materials for molding, in the present invention, as will be described later, while further adding dust, sludge, iron ore powder and the like, an inorganic binder and an organic binder, and a cement that plays a role as an auxiliary binder as necessary, for example, , Add a binder made of alumina cement, Portland cement, granulated blast furnace slag, bentonite, water glass, etc., and then knead them in a mixer (mixer), then place them in a molding machine or granulator To do. The particle size distribution and chemical composition of typical sintered powder and pre-furnace sieving powder, which are main raw materials for molding, are shown below.

  The second feature of the present invention is the selection of a 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, the binder may be a hydraulic binder such as alumina cement or Portland cement, or an inorganic binder such as blast furnace granulated slag, bentonite, or water glass.

  However, if a hydraulic binder such as cement is used, it will provide a slag-forming component in the blast furnace as described above, so the amount used is the crushing strength that can be transferred from the production site to the blast furnace. For example, 10 mass% or less (vs. molding material 100 mass%). In addition, the addition of the cement helps to maintain the shape in the low temperature region in the upper part of the blast furnace. However, the use of cement also reduces the strength significantly in the high temperature range from the middle to the lower part of the blast furnace due to the thermal decomposition of the cement hydrate, which is accompanied by pulverization in this region (middle and lower part of the blast furnace). It causes deterioration of air permeability.

  For such problems, a sticky hydrocarbon mixture such as asphalt or pitch may be mixed. However, the non-calcined agglomerate formed using such a binder evaporates at 200 ° C. However, although high-temperature strength is improved by generating gaseous carbon at a high temperature, there is a problem that the crushing strength in the low-temperature region at the upper part of the blast furnace is rather poor.

  Therefore, in the present invention, in order to overcome the problems of the above-mentioned binders such as cement and pitch, an organic binder such as molasses or a synthetic resin binder is used. These are very effective in securing the strength necessary to suppress pulverization during granulation and transfer, and maintain the action as a binder even after moisture adjustment and even after drying. And helps prevent particle collapse.

  As the synthetic resin binder used in the present invention, a phenol resin, a gum-based material that is a neutral polysaccharide, or a cellulose-based thickener can be used. Guam gum or gum arabic can be used as the gum-based material. These organic binders may be used alone or in combination with several kinds of binders. In addition to the use of the above-mentioned gum-based materials and cellulose-based thickeners, thickeners may be used. As a dispersion strengthening agent, a substance having a carboxylic acid group can be used in combination, or in combination with an inorganic binder composed of bentonite or water glass described later. In the present invention, it is particularly preferable to use a phenol resin.

  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. Here, the phenol resin precursor is phenol, o-cresol, m-cresol, p-cresol, resorcinol, catechol, pyrogallol, bisphenol A, p-tert-butylphenol, p-octylphenol, p-phenylphenol, 2, A phenolic raw material in which a hydroxyl group is added to an aromatic ring such as 5-xylenol or 3,5-xylenol is reacted with an aldehyde-based raw material such as formaldehyde, acetaldehyde, benzaldehyde, glyoxal, furfural, hexamethylenetetramine. Of these, a combination of phenol and formaldehyde is common.

  When the phenolic raw material and the aldehyde raw material are reacted, an acid or alkali catalyst is usually added. A product using an acid catalyst is called a nopolac type, and a product using an alkali catalyst is called a resol type. In the case of a combination of phenol and formaldehyde, the nopolac-type phenol resin precursor is a variety of condensates having a molecular weight of about 2000 or less in which phenol is mainly linked in a straight chain by a methylene bond. In the case of a resol type, trimethylol is used. It is a mixture of methylolphenol centered on phenol and its dimer, trimer and the like. In the present invention, both a resol type and a novolac type can be used.

  The phenol resin precursor has various forms such as an aqueous solution, an organic solvent solution, and a powder. Any of them can be used in the present invention, and a phenol resin precursor in a form suitable for each agglomeration method can be selected. . In general, the resol type self-crosslinks by heating to 150 ° C. or higher, but the novolac type requires a curing agent such as hexamethylenetetramine. What is necessary is just to add a hardening | curing agent by the method suitable for each agglomeration method. The phenol resin used in the present invention also includes a phenol-urea resin in which a part of phenols is substituted with urea.

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

  In particular, the phenol resin that enters the blast furnace as part of the constituents of the unfired agglomerated minerals is decomposed by heat and partly gasified, and carbon (pyrolysis residue) is generated in the unfired agglomerated minerals. . That is, the phenol resin has a carbon ratio (residual carbon ratio) remaining when heated to 500 ° C. or higher in a non-oxidizing atmosphere, which is about 40% by mass or more, compared with almost 0% of many resins such as acrylic and polyolefin. The high point is a characteristic binder. Therefore, the non-fired agglomerated agglomerate obtained by agglomerating phenol resin as a binder maintains the crushing strength by the binder function of the phenol resin itself from the time of charging the blast furnace to about 350 ° 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.

  The inventors conducted an experiment to confirm the effect of the phenol resin. That is, a sintered powder having a particle size of less than 5 mm was used as a raw material, and an unfired agglomerated mineral was produced under the conditions shown below as an organic binder.

(Example 1)
As a phenol resin precursor, “Resitop PL-5601” (trade name, solid content 50 mass% aqueous solution) manufactured by Gunei Chemical Co., Ltd. was used. The residual carbon ratio of the phenol resin precursor at 500 ° C. in a nitrogen atmosphere of the thermoset at 180 ° C. is 59 mass%.
In agglomeration of raw materials, an iron oxide raw material and a phenol resin precursor are mixed and granulated at room temperature using a rotary granulator, and the resulting granulated product is heated at 180 ° C. using an electric oven. The phenolic resin was heat-cured by heating for 30 minutes to produce an agglomerate.

(Example 2)
Agglomerate was produced under the same conditions as in Example 1 except that “Resitop PL-4804” (trade name, 70 mass% solid content aqueous solution) manufactured by Gunei Chemical Co., Ltd. was used as the phenol resin precursor. The residual carbon ratio at 500 ° C. in a nitrogen atmosphere of the thermosetting product at 180 ° C. of the used phenol resin precursor is 59 mass%.

(Example 3)
“Resitop PGA-2165” (trade name, powder) manufactured by Gunei Chemical Co., Ltd. was used as the phenol resin precursor. The residual carbon ratio of the phenol resin precursor at 500 ° C. in a nitrogen atmosphere of the thermoset at 180 ° C. is 73 mass%.
In agglomeration of raw materials, an iron oxide raw material and a phenol resin precursor are mixed, and 10 mass% (outer) water is added to this mixture at room temperature using a rotary granulator. Granulated. The obtained granulated product was heated at 180 ° C. for 30 minutes using an electric oven to thermally cure the phenolic resin, thereby producing an agglomerate.

(Example 4)
In accordance with Example 1, a styrene / acrylic emulsion (“Muvinyl 940” (trade name) manufactured by Nichigo Movinyl Co., Ltd.) was used as a binder, and this binder was mixed with an iron oxide raw material. The mixture was granulated at room temperature using a rotary granulator, and the granulated product was heated at 180 ° C. for 30 minutes to produce an agglomerate. The residual carbon ratio of the resin component of the used styrene / acrylic emulsion at 500 ° C. in a nitrogen atmosphere is 0.9 mass%.

(Example 5)
Portland cement was used instead of phenolic resin as a binder. The iron oxide raw material and Portland cement were mixed, water having the same mass as the cement was added, granulated at room temperature using a rotary granulator, and the granulated material was cured at room temperature for 3 days.

With respect to the unfired agglomerated minerals of Examples 1 to 5 obtained as described above, the crushing strength was measured directly or after heat treatment at a temperature of 6 levels with a particle size of about 15 mm.
In measurement of crushing strength at normal temperature (23 ° C), 200 ° C, 400 ° C, after standing at each measurement temperature for 1 hour or more in a nitrogen atmosphere, one agglomerated ore was crushed by a compression test using a universal testing machine. The load to be measured was measured. Five grains were measured under the same conditions, and the average value thereof was taken as the crushing strength.

  On the other hand, in the measurement of the crushing strength at 600 ° C., 800 ° C., and 1000 ° C., the crushing strength of the agglomerated mineral heat-treated at each temperature in a nitrogen atmosphere was measured at room temperature. The heating rate during the heat treatment was 5 ° C./min, and the holding time at the target temperature was 10 minutes. After completion of the holding time, the sample was left in a nitrogen atmosphere until the temperature reached 100 ° C. or lower. In the compression test using a universal testing machine, the load at which one agglomerated ore was crushed was measured, and 5 grains were measured under the same conditions, and the average value was taken as the crushing strength.

Table 5 shows the composition of the agglomerates of Examples 1 to 5 and the crushing strength at each temperature.
According to this, the agglomerates of Examples 1 to 5 have a crushing strength of 390 N / piece or more at normal temperature and 100 N / piece or more at each temperature other than normal temperature. In contrast, in Example 4 in which a styrene / acrylic emulsion was used as the binder, the crushing strength exceeded 390 N / piece at room temperature, but was below 100 N / piece at 400 ° C., and the shape could not be maintained above 600 ° C. It was pulverized. In Example 5 in which cement was used as the binder, the crushing strength was still below 100 N / piece at 800 ° C. or higher.
This shows that the use of a phenolic resin is recommended as the organic binder.

  In addition, in the production of the non-fired agglomerated mineral of the present invention, as described above, it includes a raw material for molding such as sintered powder and an organic binder as main components, but other components such as, for example, One or more of iron ore powder, fine powdered iron oxide, 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 producing the unfired agglomerated minerals based on the method of the present invention, first, after adding a binder such as other components and an organic binder to the mixed raw material consisting of the raw materials for molding, It forms (granulates) by adding water and stirring (kneading). Thereafter, a desired non-calcined agglomerated mineral is obtained by performing a curing treatment specific to the present invention, which will be described later in detail in Examples.

  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. Since the briquette molding machine mechanically compresses the particle group, the filling rate of the molded product increases, and the green strength (strength immediately after molding. On the other hand, cold strength refers to a certain curing period after molding. The strength of the particles after the binder is solidified) tends to increase, but the cold strength after curing depends largely on the quality and quantity of the binder, and the rolling granulation method and the compression granulation method There is no big difference between. In general, the compression granulation method has a feature that it is easy to produce a uniform particle size and property as compared with the rolling granulation method, but has a high equipment cost and repair cost.

  As described above, the granulated product needs to be cured. In general, in the case of the present invention, the granulated product mainly uses an organic binder as a binding material for binding molding raw materials such as sintered powder and pre-furnace sieve powder into pseudo particles. In addition, hydraulic binders such as cement are also used. Such a hydraulic binder is mainly used in the presence of moisture to cure agglomerated ore after molding by mainly using a hydration reaction to increase the binding strength between the raw material powders for molding. It exerts the effect of developing the strength of. Further, since the sintered powder or the like contains calcium ferrite or the like, this curing, particularly hydration curing treatment is effective even when cement or the like is not included.

Generally, as a method for expressing the strength of green agglomerated minerals using a hydration reaction, it is common to perform raw agglomerated minerals by a curing method such as yard deposition. In this curing treatment, in addition to the hydration reaction between CaO and water in the binder (CaO + H ₂ O → Ca (OH) ₂ ), CaO in the binder elutes into the moisture and becomes 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, in normal curing methods such as yard accumulation, it takes a long time (48 hours or more) to develop the required strength, and a large yard space must be secured. Carbonation reactions are often difficult to occur.

Therefore, the inventors made it possible to use a hydraulic binder such as cement, and in this case, researched a method for developing a high strength of the molded body, particularly a curing treatment method.
As a result, as a desirable curing treatment, it was 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 mineral obtained by performing such steam curing treatment exhibits a crushing strength that can sufficiently withstand handling during transportation, for example, 100 N / piece or more (5.6 MPa). 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. As a result, the hardening reaction by carbonation is accelerated, and the impact strength of the unfired agglomerated ore 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-fired agglomerated minerals, drying after curing is not particularly carried out, and the non-fired agglomerated minerals obtained after curing are charged as they are into the blast furnace as raw materials for blast furnaces. On the other hand, in the present invention, if necessary, the unbaked agglomerated ore is dried at a temperature of about 80 to 150 ° C. with a drying device or the like after curing the unburned agglomerated mineral until the blast furnace is charged. While improving the impact strength, it is preferable to maintain the air permeability in the blast furnace by reducing the content of free moisture in the unfired agglomerated mineral to 4 mass% or less, preferably 2 mass% or less.

  That is, if such a drying process is performed, the free water | moisture content in this unbaking agglomerated mineral can be evaporated. As a result, when the unfired agglomerated ore is put into a blast furnace, it does not expand and explode due to its vapor pressure (internal pressure) to be pulverized, and the air permeability in the furnace is not deteriorated.

  The unfired agglomerated mineral produced through the above-described production process compatible with 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 FIG. 5 to FIG. 7 in comparison with the sintered ore, all of which 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.

Sintering powder for return ore and raw powder before furnace (shown in Tables 1 to 4), which are raw materials for molding, alumina binder, Portland cement, blast furnace granulated slag, phenol resin (Gunei Chemical Co., Ltd.) as binders A mixed raw material to which any one or more of cash register tops PL5601) were added was molded according to a production flow as shown in FIG. 1 and subjected to a predetermined curing treatment to produce a non-fired agglomerated ore.
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 sieving powder are the same, but the sintered powder has a slightly finer particle size, and 30 mass or less is 50 mass%
The average particle size is 1.49 mm. On the other hand, the pre-furnace sieving powder has a slightly coarse particle size, 0.15 mm or less is 10 mass%, and the average particle size is 2.52 mm.

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 7 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 exceeding 5 mm, 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. .

  In addition, the “blow-out phenomenon” of the number of blow-throughs shown in Table 7 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 including an inorganic binder in addition to an organic binder as a binder.
Invention Example 2 is an example in which alumina cement is included in addition to an organic binder as a binder.
Invention Example 3 is an example in which the binder is only an organic binder.
Comparative Example 1 is an example that does not contain any organic binder.
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.

  FIG. 10 shows the porosity of the non-fired agglomerated mineral when the phenol resin binder addition is different, but the reduction reactivity is higher when the phenol resin binder is included than when the phenol resin binder is not included. Is high.

  Moreover, as can be seen from the operation results shown in Table 7, in the example in which the non-fired agglomerated ordinance suitable for the example of the present invention was charged, compared to the non-fired agglomerated mineral which is a non-compliant example shown in the comparative example, It turns out that there is little powdering during conveyance. 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 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 non-baking 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. It is a graph which shows the change of the porosity by the phenol resin content in an Example.

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 (14)

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 the forming raw material for forming the unfired agglomerated mineral, the sintered powder is included, and after the binder is mixed and kneaded with the binder containing at least an organic binder, the molding is performed, and then preliminary curing and steam curing are performed. A method for producing an ore raw material for a blast furnace, characterized in that a non-fired agglomerated ore is obtained by performing a curing process in two stages. 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 an ore raw material for a blast furnace according to claim 1 or 2, wherein the forming raw material further contains at least one of dust, sludge, and iron ore powder. The said binding material contains a cement and / or an inorganic binder other than an organic binder, The manufacturing method of the blast furnace ore raw material of any one of Claims 1-3 characterized by the above-mentioned. The method for producing a blast furnace ore raw material according to claim 4, wherein the cement is alumina cement or Portland cement. The method for producing an ore raw material for a blast furnace according to claim 4, wherein the inorganic binder is at least one of blast furnace granulated slag, bentonite, and water glass. The method for producing an ore raw material for a blast furnace according to claim 6, wherein the organic binder is molasses or a synthetic resin binder having a function as a binder even after water is evaporated. The method for producing an ore raw material for a blast furnace according to claim 7, wherein the synthetic resin binder is a phenol resin binder. The blast furnace ore raw material according to any one of claims 1 to 3, wherein the pre-curing is a treatment that is allowed to stand on a yard for 30 minutes to 5 hours at a temperature of 40 ° C or lower. Production method. The method for producing an ore raw material for a blast furnace according to any one of claims 1 to 3, 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 11, wherein drying is performed after the 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 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 13, wherein the non-fired agglomerated mineral has an RDI (reduction powdering characteristic) of 30% or less.

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