JP5130477B2 - Granulation method of iron ore raw material containing fine powder - Google Patents

Description

The present invention relates to a method for granulating an iron ore raw material containing fine powder.

When iron ore raw materials are calcined and agglomerated with a Dwytroid type sintering machine (hereinafter also referred to simply as a sintering machine) and used as a blast furnace raw material, the iron ore raw materials are produced with high productivity and yield in the sintering machine. It is important to manufacture well. For this purpose, it is important to ensure the air permeability between the iron ore materials in the sintering machine pallet charged with the iron ore materials. For this reason, the iron ore materials are granulated to ensure the air permeability. Things have been done.
Looking at the recent trends in raw materials for iron ore raw materials, high-quality iron ores that are massive and contain a large amount of iron have been depleted, and as a result, inferior iron ores containing a large amount of powder and reduced iron content can be used as iron ore raw materials. It is sought to use. The inferior iron ore is, for example, limonite, which is iron ore containing 3% by mass or more of crystal water. Moreover, as an example of inferior iron ore with much powder, in hematite, there are, for example, Yanpy ore, Denpo ore, Rio doce ore, and Carajas ore. In these, 500 μm under is 40% by mass or more, and 22 μm under is 5% by mass or more, and the powder is abundant.

As the iron ore raw material to be supplied to the sintering machine, iron ore raw material having a particle size of 1 mm over is used as a core particle, and a so-called pseudo particle in which a fine powder of 1 mm under is attached around the core particle, or There are pellets that are mainly granulated. Below, the concrete granulation method is demonstrated.
For example, Patent Document 1 discloses a method of mixing dry dust with this wet dust for the purpose of omitting drying of the wet dust obtained at an ironworks, and the water content after mixing is 10-13. It is described that after adjusting the blending amount of dry dust so as to be mass%, this mixture is granulated to produce 5-10 mm mini-pellets (pellets).
Further, Patent Document 2 discloses a method for producing pseudo particles using only water without using a binder. In producing pseudo particles, a target moisture concentration at the time of granulation of pseudo particles is set in advance. It is described that the difference between the moisture contained in the iron ore raw material and the target moisture is added.

In Patent Document 3, pseudo ore raw material having a particle size of 1 mm over, particularly 2 mm over is used as a core particle, and a fine powder of 1 mm under, especially 0.5 mm under is attached around the core particle. A method for granulating the particles is described.
This granulation is based on the premise that the moisture content of the iron ore raw material is set to 5.5 to 6% by mass, and the adjustment of the moisture content is natural moisture (for example, originally contained in the iron ore raw material). , About 4.5% by mass), when the iron ore raw material is granulated, it is further supplemented with 1.5 to 2% by mass of water.
Furthermore, when the core particles are porous and have high water absorption, after adding the amount of water necessary to saturate the amount of water that the core particles can absorb, granulation is performed by adding water necessary for granulation. To do.

Japanese Patent Laid-Open No. 62-267431 Japanese Patent Laid-Open No. 11-61281 Japanese Patent Laid-Open No. 5-39530

However, the conventional method still has the following problems to be solved.
In the case of the method of Patent Document 1, wet dust obtained at an iron mill is used, and this wet dust has, for example, a very high proportion of fine powder having an average particle size of about 1 to 3 μm, and many fine particles are present. Easy to obtain high pellet strength. For this reason, in the method of Patent Document 1, the pellet strength is satisfied when the iron ore raw material containing about 60% by mass of particles over 500 μm exists like the iron ore raw material that the present application intends to granulate. It does not become as high as possible, and even when a binder is used, high strength cannot be easily obtained.
Therefore, the method of Patent Document 1 cannot improve the pellet strength of the iron ore raw material containing particles having a large particle size, which is a subject of granulation in the present application.

Patent Document 2 focuses on the effect of the amount of water on the granulation of the iron ore raw material. In the amount of water, the water originally contained in the iron ore raw material and the amount added during granulation of the iron ore raw material are disclosed. There is no distinction with the moisture to be. For this reason, there is a problem that the strength of the granulated pellet becomes unstable due to the new knowledge of the present application, which will be described later, that is, the influence of whether or not moisture is wet on the particle surface of the iron ore raw material.
In addition, since the method of Patent Document 2 is a method of manufacturing pseudo particles having a small particle size, this method is larger in particle size than the pseudo particles (for example, average particle size) as in the pellets targeted by the present application. When applied to the production of pellets having a diameter of 3 mm or more, there is a problem that the pellet strength is insufficient.

In the case of the method of Patent Document 3, when the fine powder content in the iron ore raw material to be granulated increases as in the raw material trend of the iron ore raw material described above, the thickness of the fine powder attached to the core particle increases, When transporting to a sintering machine pallet of a sintering machine or when charging into a sintering machine pallet, there is a problem that pseudo particles collapse.
In addition, according to the knowledge of the inventors of the present application, in order to prevent the above-described remarkable collapse of the pseudo-particles, it is necessary to make the adhesion thickness of the fine powder to the core particles be about 300 μm or less. Although pseudo particles that can satisfy such an adhesion thickness can be granulated by sieving the iron ore raw material, there is a problem that the fine powder content becomes excessive in recent raw material trends.

Furthermore, in Patent Document 3, in view of the fact that moisture is absorbed inside the porous iron ore raw material, when granulating, the amount of moisture necessary to saturate the amount of moisture that can be absorbed by the core particles is set. Although added, when this method is used, there is a problem that the strength of the granulated material is not stable.
As described above, in Patent Document 3, granulation is performed by fixing the potential natural moisture of the iron ore raw material to about 4.5% by mass and adjusting the moisture with respect to the iron ore raw material to 5.5 to 6% by mass. However, the properties of the iron ore raw material, that is, the degree of porosity of the iron ore raw material is generally not stable, and the amount of water to be saturated is different, so the amount of water according to the degree of porosity is not adjusted. . For this reason, it will be in the supersaturated state in which the excess water | moisture content which is not saturated exists in an iron ore raw material, or it will be in the unsaturated state in which an iron ore raw material is not saturated, As a result, the intensity | strength of a granulated material will become unstable. Further, according to the knowledge of the inventors of the present application, even when the saturated water content is measured in advance for each ore type of the iron ore raw material, for example, when the particle size configuration changes, the saturated water content changes even within the same ore type. Therefore, it is known that it is difficult to stabilize the strength of the granulated product.

In addition, under the above situation, assuming the case of granulating a high-strength pellet as in the present application, there is the following problem. In general, pellets are granulated by rolling a granulated product (for example, a particle size of about 0.5 to 1 mm) at the initial stage of granulation to increase the particle size. However, if there is an iron ore raw material that is in a supersaturated or unsaturated state with a saturated water content as a boundary, particle size growth due to rolling cannot be expected, and rather the granulated material collapses, which is not preferable.
In order to improve these situations, it is conceivable to increase or decrease the amount of water added during granulation while looking at the granulation status of the iron ore raw material. Does not wet easily (poor wettability). For this reason, the strength of the granulated product in the granulation process cannot be increased to the target level, the collapse cannot be suppressed, and a new granulated product is made again using the granulated product after the collapse as a core. Therefore, a great effect cannot be expected for the particle size growth of the granulated product.

The present invention was made in view of such circumstances, and when granulating inferior iron ore raw material containing a lot of fine powder, on the premise that about 60% by mass of iron ore raw material having an average particle size over 500 μm exists, An object of the present invention is to provide a method for granulating an iron ore raw material containing fine powder capable of producing a high-strength pellet by overcoming the moisture absorption effect of the iron ore raw material and giving a finer control of the amount of water. .

Granulation process of iron Ishihara fees including fines according to the present invention along the object, 500 [mu] m under 40 mass% or more and 22μm under is 5 mass% or more, own the iron Ishihara fee of water content containing fines After controlling within a fixed range, the iron ore raw material is granulated by adding granulation moisture together with a binder, and a pellet having an average particle size of 3 mm or more is produced ,
The binder is a dispersant, and the predetermined amount range is 5.5% by mass or more and 8.5% by mass or less in terms of moisture of the iron ore raw material after adding the dispersant and the moisture for granulation. The dispersant is mixed with part or all of the granulating moisture, and the amount of the dispersant is set to 0.001% by mass or more and 1% by mass or less with respect to the amount of the iron ore raw material .
Moreover, the granulation method of the iron ore raw material containing fine powder according to the present invention includes a predetermined amount of moisture contained in the iron ore raw material containing fine powder, in which 500 μm under is 40% by mass or more and 22 μm under is 5% by mass or more. After controlling the inside of the iron ore raw material, it is a method of adding granulation moisture together with a binder and granulating to produce pellets having an average particle size of 3 mm or more,
The binder is an adhesive binder, and the predetermined amount range is 4.0% by mass or more and 8.0% by mass or less in terms of moisture of the iron ore raw material after adding the adhesive binder and the granulating moisture. The adhesive binder is mixed with a part or all of the granulating moisture, and the amount of the adhesive binder is 0.1% by mass or more and 5% by mass or less based on the amount of the iron ore raw material.
Furthermore, the granulation method of the iron ore raw material containing fine powder according to the present invention includes a predetermined amount of moisture contained in the iron ore raw material containing fine powder in which 500 μm under is 40% by mass or more and 22 μm under is 5% by mass or more. After controlling to within the range, the iron ore raw material is added with granulation moisture together with a binder, and granulated to produce pellets having an average particle size of 3 mm or more,
The binder is quick lime, and the predetermined amount range is 1.0% by mass or more and 9.0% by mass or less in terms of moisture of the iron ore raw material after adding the quick lime and the moisture for granulation, The amount of quicklime is 0.1% by mass or more and 2% by mass or less with respect to the iron ore raw material amount.

In the granulation method of the iron Ishihara fees including fines according to the present invention, the addition of humidity iron ore raw material containing moisture than 3 wt% greater than 0 or 0 to the iron ore raw material before addition of the granulating water Therefore, it is preferable to control the moisture content of the iron ore raw material within the predetermined amount range .
In the granulation method of the iron Ishihara fees including fines according to the present invention, the addition of humidity iron ore raw material containing moisture 7% or more and 12 mass% or less in the iron ore raw material before addition of the granulating water Therefore, it is preferable to control the water content of the iron ore raw material within the predetermined amount range .
In the granulation method of the iron Ishihara fees including fines according to the present invention, by adding water to the iron ore raw material before addition of the granulating water, a water content of the iron Ishihara charges within the predetermined weight range It is preferable to control .

In the granulation method of the iron ore raw material containing fine powder according to the present invention, the iron ore raw material to which the water is added is pulverized after the water is added and before the iron ore raw material is granulated. It is preferable.
In the granulation method of the iron ore raw material containing fine powder according to the present invention, it is preferable that the humidity-controlled iron ore raw material has an iron ore raw material under a sieve obtained by sieving and sorting the iron ore raw material after the granulation treatment.
In the granulation method of the iron ore raw material containing fine powder according to the present invention, the moist iron ore raw material preferably has an iron ore raw material obtained by further drying the iron ore raw material after the granulation treatment.
In the granulation method of the iron ore raw material containing fine powder according to the present invention, the humidity-controlled iron ore raw material is added to the iron ore raw material and pulverized together with the iron ore raw material before the addition of the granulating moisture. It is preferable.
In the granulation method of the iron ore raw material containing fine powder according to the present invention, the moist iron ore raw material may have a dry dust collection powder generated when the iron ore raw material after the granulation treatment is further subjected to a drying treatment. preferable.

In the granulation method of the iron ore raw material containing fine powder according to the present invention, the iron ore raw material is preferably a blended iron ore obtained by mixing two or more types of iron ore raw materials.

The method of granulating an iron ore raw material containing fine powder according to claims 1 to 12 , wherein the iron ore raw material contains 40% by mass or more of particles under 500 μm, so that the amount of particles over 500 μm having large pores is adjusted and wetted It is possible to control the fluctuation of the amount of moisture that gets wet on the surface of the iron ore raw material.
Moreover, since the iron ore raw material contains 5% by mass or more of 22 μm-under particles, particles having almost no pores can be used, the wettability can be controlled, and fluctuations in the amount of moisture that gets wet on the surface of the iron ore raw material can be suppressed. The pellet strength by the fine powder can be improved.
And before performing a granulation process, since the moisture content of an iron ore raw material is controlled within the predetermined amount range, for example, according to the property (namely, degree of porosity) of an iron ore raw material or the particle size composition of an iron ore raw material Controlling the wettability of the iron ore raw material, it is possible to achieve moderate wetting on the surface.
Further, since the binder and granulation moisture are added to the iron ore raw material and granulated, the granulation moisture is not unevenly distributed in a part of the iron ore raw material, and the iron ore raw material is moderately distributed over the entire iron ore raw material. Demonstrates wettability, and the entire iron ore raw material gets wet moderately. For this reason, the binder added with the moisture for granulation also spreads among the particles of the iron ore raw material, and the effect of solid cross-linking formation by the binder can be obtained over the entire iron ore raw material.
As a result, it is possible to overcome the moisture absorption effect of iron ore raw materials having an average particle size of over 500 μm over about 60% by mass and to control the amount of water more precisely, and to produce high-strength pellets. Can be manufactured.

In particular, the method for granulating an iron ore raw material containing fine powder according to claim 1 uses a dispersant as a binder and defines an optimum water amount range of the water content of the iron ore raw material. It also plays an important role in the granulation process, and can sufficiently contribute to the formation of solid bridges between the iron ore raw material particles. Moreover, since the density | concentration of the dispersing agent with respect to an iron ore raw material is prescribed | regulated, an iron ore raw material can be granulated, obtaining the effect of a dispersing agent.
In the granulation method of the iron ore raw material containing the fine powder according to claim 2, since the adhesive binder is added as the binder, the particles of the iron ore raw material can be bonded to each other by the adhesiveness of the adhesive binder itself. In addition, in adhesive binders that use adhesiveness for granulation, wetting of the moisture for granulation onto particles whose surface is wetted with iron ore raw material plays an important role in the granulation process. Since there is also the adhesiveness of the binder itself, the width of the optimum water amount range when using the adhesive binder can be made larger than the optimum water amount range when using the dispersant. Moreover, since the density | concentration of the adhesive binder with respect to an iron ore raw material is prescribed | regulated, an iron ore raw material can be granulated, obtaining sufficient adhesiveness.
Since the granulation method of the iron ore raw material containing fine powder according to claim 3 uses quick lime (main component is CaO) as a binder, when quick lime is dissolved in water, the fact that water becomes alkaline is utilized. The granulation effect of the iron ore raw material can be obtained. Here, since the granulation effect of the iron ore raw material can be obtained if an alkaline aqueous solution is present, the optimum water amount range of the water content of the iron ore raw material can be made larger than the optimum water amount range of the adhesive binder, The accuracy of the amount of water can be relaxed, and workability is also improved. Moreover, since the addition amount of quick lime with respect to an iron ore raw material is prescribed | regulated, a granulation effect can be acquired economically, without adding quick lime excessively.
Granulation process of iron Ishihara fees including fines according to claim 4, by addition of iron ore raw material containing moisture is no or little humidity iron ore raw materials that put before the addition of the granulating water, iron ore Since the moisture content of the raw material is controlled within a predetermined amount range, it is easy to adjust the moisture content of the iron ore raw material .
Granulation process of iron Ishihara fees including fines of claim 5, by adding the content juicy humidity iron ore raw material in the iron ore raw material that put before the addition of the granulating water, iron Ishihara fees Since the moisture content is controlled within a predetermined range, it is easy to adjust the moisture content of the iron ore raw material.
Granulation process of iron Ishihara fees including fines of claim 6, by the addition of water to the iron ore raw material that put before the addition of the granulating water, a water content of iron Ishihara fee within a predetermined weight range Since it is controlled, it is easy to adjust the moisture content of the iron ore raw material.

The granulation method of the iron ore raw material containing fine powder according to claim 7 pulverizes the iron ore raw material to which moisture has been added before granulating the iron ore raw material. Can promote wetting.
The granulation method of the iron ore raw material containing fine powder according to claim 8 , since the humidity-controlled iron ore raw material has an iron ore raw material under the sieve obtained by screening and sorting the iron ore raw material after the granulation treatment, Since the composition and particle size composition are the same as the previous iron ore raw material, fluctuations in quality and operating conditions can be suppressed, and unnecessary iron ore raw material can be reused.

The method of granulating an iron ore raw material containing fine powder according to claim 9 is intended to improve the strength of the pellet because the humidity-controlled iron ore raw material has an iron ore raw material obtained by further drying the iron ore raw material after the granulation treatment. And the amount of moisture contained in the iron ore raw material can be easily controlled.
In the granulation method of the iron ore raw material containing fine powder according to claim 10 , the moisture-controlled iron ore raw material is pulverized together with the iron ore raw material before the addition of the moisture for granulation. Uneven distribution can be suppressed.
In the granulation method of the iron ore raw material containing fine powder according to claim 11 , the humidity-controlled iron ore raw material has a dry dust collection powder obtained by collecting the fine powder scattered during drying, so that the resources can be effectively used. At the same time, it is environmentally preferable.

The method for granulating an iron ore raw material containing fine powder according to claim 12 uses a blended iron ore that is currently available as an iron ore raw material, so that the effect of producing a high-strength pellet more stably can be obtained. Can do. This is a method in which the present invention eliminates the instability of the particle size distribution by adjusting the particle size of the iron ore raw material, and suppresses fluctuations in the degree of porosity by using a large amount of fine powder. Furthermore, even if the particle size distribution and the degree of porosity are not constant, these fluctuation factors can be suppressed to suppress the fluctuation of the granulated pellet strength.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is explanatory drawing of the granulation method of the iron ore raw material containing the fine powder which concerns on one embodiment of this invention, FIG. 2 (A)-(C) is the iron ore particle | grains which respectively comprise an iron ore raw material. 3A to 3C are explanatory diagrams showing the granulation mechanism of the iron ore raw material when a dispersant is used as the binder, and FIG. 4 is the types of binder and iron ore. It is explanatory drawing shown about the influence which the moisture content of a stone raw material has on pellet strength.

As shown in FIG. 1, the granulation method of the iron ore raw material containing the fine powder according to one embodiment of the present invention includes an iron ore containing fine powder in which 500 μm under is 40% by mass or more and 22 μm under is 5% by mass or more. This is a method for producing pellets having an average particle diameter of 3 mm or more by controlling the moisture content of the stone raw material within a predetermined amount range and then adding granulation moisture to the iron ore raw material together with a binder. This iron ore raw material (hereinafter also simply referred to as a raw material) is composed of a large number of iron ore particles (hereinafter also simply referred to as particles).

In the present embodiment, the following definitions are assumed.
Let the amount of the dried iron ore raw material not containing water be Gm (kg). In addition, in the case of the iron ore raw material containing crystal water, the amount of iron ore raw material contains crystal water. This is because crystal water cannot be easily removed.
Let Gt (kg) be the amount of moisture (hereinafter, also simply referred to as retained moisture) retained by the iron ore raw material during granulation. Therefore, Gt (kg) is the amount G1 (kg) of the moisture content of the iron ore raw material (hereinafter also referred to simply as moisture content) before adding the granulation moisture, and the granulation moisture added during the granulation treatment. It is the sum of G2 (kg).
The amount of binder added is Gb (kg). In addition, the addition amount of a binder is very small with respect to an iron ore raw material.

Here, the moisture content is the moisture contained in the iron ore raw material until the iron ore raw material reaches the granulation process in which the granulation process is performed, and water droplets adhere to the iron ore raw material. Most of the water is wet (familiar) with the surface of the iron ore raw material particles after a certain period of time. Specific examples include those caused by rainwater in the storage yard of iron ore raw materials and watering for the purpose of preventing dusting, and those by watering for preventing dusting during transportation (for example, on a belt conveyor). .
Also, the moisture for granulation is moisture added to the iron ore raw material together with the binder, and when the binder is added, the iron ore raw material is granulated immediately, so that the particle surface of the iron ore raw material does not get wet. Moisture (unfamiliar). In the case where the binder is an aqueous solution, for example, if it is a binder using water, such as an aqueous solution binder or a water-added colloidal binder, this moisture is also included in the moisture for granulation.

From the above, the dry iron ore raw material, the retained moisture, and the retained moisture ratio Rt (mass%), the contained moisture ratio R1 (mass%), and the granulation moisture ratio R2 (mass%). ) Are each represented by the following equation.
Rt = Gt / (Gt + Gm + Gb) ≈Gt / (Gt + Gm)
R1 = G1 / (Gt + Gm + Gb) ≈G1 / (Gt + Gm)
R2 = G2 / (Gt + Gm + Gb) ≈G2 / (Gt + Gm)
Here, Gt = G1 + G2 and Rt = R1 + R2.
In addition, R1 is the ratio of the moisture content of the iron ore raw material, and if it is normal, what is necessary is just to show the ratio with respect to the dried iron ore raw material and retained moisture, but in this Embodiment, the moisture for granulation to add is shown. The ratio to the total amount considered is shown.
Moreover, the addition ratio of the binder with respect to an iron ore raw material is represented by the following formula | equation.
Gb / Gm × 100 (mass%)

First, the background to the present invention will be described.
As described above, when using an inferior iron ore containing a large amount of fine powder as an iron ore raw material and producing only pseudo particles having a small particle size from the iron ore raw material, the amount (thickness) of fine powder attached to the core particles is, for example, Increase to over 300 μm. As a result, the pseudo particles collapse in the conveying process to the sintering machine pallet or in the sintering machine pallet, the air permeability in the sintering machine pallet deteriorates, and the productivity and yield of the sintering machine are reduced. Causes it to get worse.
For this reason, the pseudo particles may be produced with a fine powder adhesion thickness of 300 μm or less, but in this case, handling of the fine powder as a residue becomes a problem.
From the above, the current raw material trend requires that the increased fine powder content be granulated so as not to cause deterioration in air permeability, and for this reason, the fine powder content should be granulated as pellets that are not pseudo particles. Is preferred.

In order to eliminate the cause of the deterioration in air permeability, it is preferable that the average particle size of the pellets mixed and sintered with the pseudo particles is at least 3 mm or more, more preferably 5 mm or more.
On the other hand, although the upper limit of the average particle diameter of the pellet is not specified, it is preferable that the upper limit is about 12 mm. This is because if the average particle size exceeds 12 mm, the inside of the pellet is unsintered, and the strength of the sintered ore produced by the sintering machine decreases.
There is a demand for a technique for stably producing pellets having the above average particle diameter with strength capable of suppressing the collapse thereof, and the following two methods are mentioned as the production method.
(1) In the particle size distribution of the iron ore raw material to be granulated, the proportion of finer fines, for example, 22 μm under, is increased.
(2) A binder is used.
In the present invention, (2), which is a method of effectively using a binder mainly, was studied.

As a granulation technique using a binder, for example, many types of binders, moisture contained in the iron ore raw material at the time of granulation, or a particle size composition of the iron ore raw material have been proposed. The inventors of the present application have a problem that the strength may not be stable even when the height of the film becomes high.
Here, the result of intensive studies by the inventors of the present invention on the cause of unstable granulation strength will be described below.
Even if the ratio of the moisture held by the iron ore raw material at the time of granulation, that is, the ratio of the retained moisture (Rt), the moisture brought into the granulation process constituting this moisture, that is, the ratio of the contained moisture (R1). When the ratio of moisture added during granulation with the binder, that is, the ratio of the moisture for granulation (R2) varies, particularly when the ratio of the moisture content varies, it has been newly discovered that the pellet strength varies. . This will be described in detail below.

The following mechanism was conceived as the reason why the pellet strength fluctuates.
Ideally, the binder should spread throughout the iron ore raw material and be evenly present on the particle surface of the iron ore raw material, and have an initial effect as a binder. For this purpose, it is effective to allow the binder to exist together with the moisture for granulation that easily flows between the particles without getting wet on the particle surface of the iron ore raw material, and further, a granulation step for performing a granulation process It is effective to provide a kneading step in the initial stage of kneading the iron ore raw material. In this kneading step, it is possible to use a kneader that is generally used frequently in the pretreatment step of the sintering raw material.
However, even with these, it has come to be seen that the binder does not spread over the iron ore raw material and the pellet strength is not stable at a high level.
As described above, it was considered that the effect of the binder cannot be exhibited even by kneading because the properties of the iron ore raw material have changed to those containing a lot of fine powder.

Furthermore, the following was considered as a cause of the unstable granulation strength.
In conventional granulation, when the iron ore raw material is granulated while keeping the retained moisture at the time of granulation constant, the proportion (R1) of the moisture content constituting the retained moisture proportion (Rt) and the proportion of moisture for granulation ( R2) was not constant. For example, since the ratio of moisture content (R1) increases during rainfall, the ratio of granulation moisture (R2) must be lowered.
In such a case, at the time of granulation of the iron ore raw material, as described above, most of the contained moisture is wetted on the particle surface of the iron ore raw material, and the effect of thoroughly spreading the binder into the iron ore raw material cannot be expected. On the contrary, it is considered that the moisture derived from the contained moisture can be an inhibiting factor for spreading the binder.
Moreover, the moisture derived from the moisture for granulation is present together with the binder, and has an effect of spreading the binder throughout the iron ore raw material by granulation operation (including kneading) before wetting the particle surface of the iron ore raw material. Is. However, in the case described above, since the ratio of retained moisture is constant, the ratio of moisture for granulation is reduced, and the effect of spreading the binder to the entire iron ore raw material is reduced.

On the contrary, when using a dry iron ore raw material without rain, the ratio of moisture for granulation (R2) is increased because the ratio of moisture content (R1) is small.
In such a case, since the ratio of the moisture content is small, the portion of the iron ore raw material that is not wet with water increases, and even if kneading is performed by increasing the proportion of moisture for granulation, The portion where the moisture for granulation gets wet on the particle surface cannot be easily increased. For this reason, the binder effect is low on the particle surface where no water is present, and it is difficult to obtain an improvement in the initial pellet strength by the binder.
Furthermore, when the iron ore raw material is granulated using a binder, the amount of moisture increases compared to the amount of binder to be added, so that the binder is diluted, and the effect of the obtained binder is reduced. .

The above shows an example in which the proportion of retained water (Rt) is constant, but not limited to this example, the proportion of contained moisture (R1) and the proportion of moisture for granulation (R2), particularly the proportion of contained moisture The present inventors have conceived that (R1) is closely related to the binder effect, and unless these are controlled within a predetermined range, the strength of the pellet becomes unstable.
Here, referring to FIGS. 2A to 2C, when the moisture derived from the contained moisture is small (A), when the moisture derived from the contained moisture is appropriate (B), and when the moisture derived from the contained moisture is Each case (C) will be described. 2A to 2C, the moisture content is indicated as W1, and the moisture for granulation is indicated as W2.

As shown in FIG. 2 (A), when the moisture derived from the contained moisture is small, the area of the iron ore particles wet with the moisture derived from the contained moisture is small before the addition of the moisture for granulation and the binder (FIG. 2 ( A) Left figure). For this reason, the moisture for granulation and the binder are easy to spread throughout the iron ore raw material, but the iron ore particles that are not wet with the contained moisture are not easily wetted with the granulation moisture, so the effect of the binder is difficult to be exhibited. (Right figure of FIG. 2 (A)).
In addition, due to the difference in specific gravity between the iron ore particles, the granulation moisture and binder may be unevenly distributed at the top of the iron ore raw material, and the granulation moisture and binder may not be distributed throughout the iron ore raw material. .

In addition, as shown in FIG. 2B, when the moisture derived from the contained water is appropriate, there are iron ore particles whose surface is moderately wet and iron ore particles which are not moderately wet (FIG. 2 ( (B) Left figure). For this reason, the moisture for granulation and a binder spread over the whole iron ore raw material, and the moisture for granulation and a binder become easy to get wet on the surface of the iron ore particle wet with the containing moisture (the right figure of FIG. 2 (B)). . Therefore, the effect of the binder is easily exerted on the entire iron ore raw material.
And as shown in FIG.2 (C), when there is much water | moisture content derived from a containing water | moisture content, before the addition of the water | moisture content for granulation or a binder, there are too many areas where the surface of an iron ore particle is wet with the containing water | moisture content (FIG. 2 (C) left figure). For this reason, after the moisture for granulation and the binder are added, the moisture for granulation (including the binder) only penetrates only a part of the entire iron ore raw material (particularly, the surface to which the moisture for granulation is added). It becomes difficult to reach the entire iron ore raw material (the right figure of FIG. 2 (C)). Therefore, in a normal stirring process, it is difficult to spread the binder over the entire iron ore raw material, so that the effect of the binder is hardly exhibited over the entire iron ore raw material.

As is clear from the above description, appropriate amounts of wet and non-wet water exist between the iron ore particles by controlling the water content of the contained water and granulating water. It is important to make it.
In particular, with regard to the contained moisture, there is a problem that the amount of moisture wetted on the particle surface can vary because the moisture is taken into the iron ore particles by the pores present in the iron ore particles.
A method for granulating an iron ore raw material containing fine powder according to an embodiment of the present invention obtained based on the above knowledge will be described with reference to FIG.

After the moisture content of the iron ore raw material containing fine powder is controlled within a predetermined range, granulation treatment is performed by adding granulation moisture to the iron ore raw material together with a binder.
Iron ore raw materials are conventionally called by brand name, for example, lobe river ore, maramamba ore, high phosphorus blockman ore, hamasley ore, yanpy ore, denpo ore, riodose ore, and carajas ore. One or more of the raw materials can be used. Iron ore raw materials tend to have a constant component value, particle size distribution, degree of porosity, and the like for each brand.

In recent years, blended iron ore blended with multiple brands at the mine has come out in the market, but this blended iron ore has the above-mentioned particle size distribution and porousness even if the above-mentioned component values are constant. The degree may not be constant, and the granulation strength may become unstable. In the present invention, by adjusting the particle size, the instability of the particle size distribution is eliminated, and a lot of fine powder is used, so that the degree of porosity (for example, the volume of pores per unit amount of iron ore raw material is cc / g The fluctuation of the granulation strength is suppressed by suppressing these fluctuation factors. For this reason, it is still more preferable to grind | pulverize with a grinder (for example, a pair of roller opposingly arranged with a clearance gap) before the process of granulating an iron ore raw material.
Therefore, by applying the method of the present invention to the granulation method of blended iron ore, the effect of producing a high-strength pellet more stably can be obtained remarkably.

This iron ore raw material contains iron ore particles having an under 500 μm under 40 mass% and an under 22 μm under 5 mass%.
The pores of iron ore particles (including gaps and spaces in the particles such as cracks) are present in relatively large particles, particularly those having a particle size over 500 μm. Therefore, it was considered that the fluctuation of the amount of water wetted on the surface of the iron ore particles described above can be suppressed by increasing the proportion of the particles of 500 μm or less as the iron ore raw material for granulating the pellets.
Further, it was found that the iron ore particles having a finer fine particle content of 22 μm or less have almost no pores, and if a predetermined amount of particles of 22 μm or less are present, the above-described fluctuation suppression is also positively affected. .

Therefore, in order to realize a mechanism that suppresses fluctuations in the amount of moisture wetted on the iron ore particle surface, an iron ore raw material containing fine powder having a 500 μm under 40 wt% or more and a 22 μm under 5 wt% or more should be used. I knew it was good.
In addition, in recent raw material trends, when producing pseudo particles that do not deteriorate the productivity of a sintering machine having a fine powder adhesion thickness of 300 μm or less on the core particles, the fine powder content becomes surplus and the 500 μm under is 40% by mass or more, and It becomes easy to obtain an iron ore raw material having a 22 μm under 5 mass% or more. Furthermore, it becomes easier to obtain iron ore particles of 22 μm or less by performing a mild pulverization process on the surplus iron ore raw material.

Here, the upper limit of the ratio of particles having a size of 500 μm or less is not particularly defined. For example, when the mass is 100% by mass, the iron ore raw material may be pulverized. 500 μm-under particles are preferred because the effect of pores is reduced as the proportion is increased, and the strength of the granulated product is stabilized at a high level.
The upper limit of the ratio of 22 μm under particles is not particularly defined, but this is also preferable as the ratio is increased because the influence of pores is reduced and the strength of the granulated product is stabilized at a high level.
In addition, when the proportion of the 22 μm under particles is 5% by mass or more, in order to obtain the effect of the binder added together with the granulating moisture, it is more preferable to adjust the moisture content ratio (R1) to a predetermined amount range in advance. It becomes important. This is due to the fact that wetting of water on the surface of fine 22 μm particles is difficult to achieve on the entire iron ore raw material. Moreover, since pellet strength will improve if a fine powder content increases, pellet strength can be made high by making the ratio of 22 micrometer under into 5 mass% or more.

When granulating the iron ore raw material, it is necessary to control the ratio of water content (R1) in the iron ore raw material within a predetermined range before the granulating process. This is used in the granulating process. The optimum range varies depending on the type of binder to be used. First, the type and amount of binder used will be described.
As the binder, a dispersant, an adhesive binder, or quicklime is used.
In addition, the dispersing agent used for a binder is described in Unexamined-Japanese-Patent No. 2003-155525, for example.
The solid content (active ingredient) amount of this dispersant is 0.001% by mass or more and 1% by mass or less (preferably the lower limit is 0.005% by mass and the upper limit is 0.5% by mass with respect to the amount of the iron ore raw material). ) Is preferable.
Here, when the solid content of the dispersant is less than 0.001% by mass, the effect of the dispersant is not obtained, and the granulation effect of the iron ore raw material cannot be obtained. On the other hand, when the solid content of the dispersant exceeds 1% by mass, the whole becomes sticky, and as a result, the granulation of the iron ore raw material may not be successful.

Moreover, the adhesive binder used for a binder is what bonds particle | grains by the adhesiveness of adhesive binder itself, for example, bentonite, lignin sulfite (pulp waste liquid), starch, sugar, molasses, water glass, There are cement, gelatin, corn starch and the like.
The amount of the adhesive binder is within the range of 0.1% by mass or more and 5% by mass or less (preferably the lower limit is 0.05% by mass and the upper limit is 3% by mass) with respect to the amount of the iron ore raw material. preferable.
Here, when the amount of the adhesive binder is less than 0.1% by mass, the amount becomes too small, the adhesiveness is insufficient, and the granulation effect of the iron ore raw material cannot be obtained. On the other hand, when the amount of the adhesive binder exceeds 5% by mass, the amount becomes too much and the whole becomes sticky, and as a result, the granulation of the iron ore raw material may not be successful.

And since the main component is CaO, the quick lime used for a binder can acquire the granulation effect of an iron ore raw material using that water becomes alkaline when quick lime melt | dissolves in water. The iron ore raw material particles generally tend to be positively charged, but in an alkaline aqueous solution (pH of about 7 to 9), the charge becomes zero, and the particles are easily physically adsorbed to obtain a granulation effect.
The amount of quicklime is 0.1% by mass or more and 2% by mass or less (preferably the lower limit is 0.5% by mass and the upper limit is 1.5% by mass) with respect to the amount of the iron ore raw material. preferable.
Here, when the quantity of quicklime is less than 0.1 mass%, the quantity becomes too small and the granulation effect of an iron ore raw material cannot be acquired. On the other hand, when the amount of quicklime exceeds 2% by mass, the amount becomes too large, and the effect of making the charge of the particles zero is saturated, so that quicklime is used wastefully.

Next, the optimum value range of the ratio (R1) of moisture content, that is, the predetermined amount range is shown for each type of each binder described above.
When a dispersant is used as the binder, the moisture content is 5.5% by mass or more and 8.5% by mass or less (7.0 ±) in terms of the moisture content of the iron ore raw material after adding the binder and moisture for granulation. 1.5 mass%), and when using an adhesive binder, the moisture content is 4.0 mass% or more and 8.0 mass% or less (6.0 ± 2.0 mass%), and quick lime is used. Is preferably 1.0% by mass or more and 9.0% by mass or less (5.0 ± 4.0% by mass).
Moreover, the ratio (R2) of the moisture for granulation is 1.0 mass% or more and 5.0 mass% or less (preferably, a minimum is 2.0 mass% and an upper limit is 4.0 mass%).
First, a granulation mechanism (granulation mechanism) when a dispersant is used as a binder will be described with reference to FIGS.

As shown in FIG. 3A, before the granulation moisture and the dispersant come into contact with the iron ore particles, extremely small fine particles (for example, 22 μm under) are taken into the granulation moisture containing the dispersant. In this granulation moisture, fine particles under 22 μm are dispersed.
Next, as shown in FIG. 3 (B), immediately after the moisture for granulation and the dispersant come into contact with the iron ore particles, the moisture for granulation containing the dispersant and fine particles under 22 μm between the iron ore particles. Wets the particle surface. At this time, since the moisture content is present on the surface of the iron ore particles, the moisture for granulation is easily wetted on the surface of each particle. That is, when the moisture content is too small, the number of cases where the moisture for granulation including the dispersant and the fine particles under 22 μm is not wetted on the surface of the iron ore particles increases.

Then, as shown in FIG. 3 (C), after the granulation moisture and the dispersing agent are wetted on the surface of the iron ore particles, as the granulation moisture wets the particle surface, The wetting width shown in FIG. At this time, since the fine particles having an under 22 μm are uniformly dispersed in the granulating water by the dispersant, they are concentrated in the granulating water between the particles.
For this reason, finally, fine particles under 22 μm remain in a shape that connects the particles (cross-linking), and connects the particles (effect of solid cross-linking generation). When the moisture content is excessive, fine particles having a size of 22 μm or less in the moisture for granulation flow to the particle surface, and the wetting width is not reduced, so that solid cross-linking between particles is difficult to be generated.
Granulation of the iron ore raw material proceeds through the above-described processes.
As is clear from the above, it is important to adjust the moisture content within a predetermined amount range, since a small amount of moisture content affects the effect of the binder (generation of solid crosslinking).

In addition, the adhesive binder binds the particles to each other due to its own adhesiveness. As described above, in the granulation with a dispersant, wetting of the moisture for granulation on the particles whose moisture content is wet on the surface plays an important role in the granulation process, but the adhesiveness is used for granulation. For binders, this function is not as important as the dispersant. For this reason, the width (± 2.0) of the optimum water amount range of the moisture content of the adhesive binder is larger than the optimum water amount range (± 1.5) of the dispersant.
And, as described above, quick lime has zero charge in an alkaline aqueous solution, and particles are easily physically adsorbed, and a granulation effect is obtained. The width (± 4.0) of the optimum water amount range of the contained water is larger than the width (± 2.0) of the optimum water amount range of the adhesive binder.

Here, the influence which the kind of binder and the moisture content of the iron ore raw material have on the pellet strength will be described with reference to FIG.
The produced pellets are produced by granulating an iron ore raw material containing 40% by mass of particles having 500 μm under and 5% by mass of particles having 22 μm under. In addition, the used binder and the moisture content at that time are the following conditions.
(A) When polyacrylic acid soda (concentration: 0.2 mass%) is used as a dispersant, the moisture for granulation is adjusted to 2.5 mass% and 3.5 mass%, respectively.
(B) When corn starch (concentration: 1.0% by mass) is used as the adhesive binder, the moisture for granulation is adjusted to 2.5% by mass.
(C) When quicklime (concentration of 1.0% by mass) is used, the moisture for granulation is adjusted to 2.5% by mass.

As apparent from FIG. 4, by adjusting the water content within the optimum water amount range according to the type of binder, the pellets are 20 N (20 N / 10 mmφ / 1 per 10 mm diameter pellet, which is an indicator of pellet strength). It was confirmed that the above strength could be achieved. In addition, about the dispersing agent, when the moisture for granulation is 3.5 mass%, there is a part which becomes partially less than 20N, but this pellet strength is one index, for example, the particle size of the iron ore raw material There is no problem because the pellet strength can be achieved also by the configuration.
The index of pellet strength was set based on the following view.
In order to ensure productivity in the sintering machine, it is necessary to increase the strength (crushing strength) of the pellets to an appropriate value and suppress the generation of fine powder due to the collapse of the pellets. For this reason, in consideration of the fact that this required strength is not a problem even when the number of times of transfer of the belt conveyor for conveying the pellets is 5 times (equivalent to the actual machine connection), the knowledge of the inventors of the present application indicates that the pellets have a diameter of 10 mm. The strength of 20N (20N / 10mmφ / 1 piece) or more per piece is required.

It is preferable to adjust the moisture content of the iron ore raw material within the respective optimum amount ranges according to the type of binder used. In addition, it is good to use the following method for adjustment of this moisture content.
When reducing the moisture content of the iron ore raw material before the addition of the granulating moisture, it is preferable to add a conditioned iron ore raw material containing 0 or more than 0 and 3% by mass or less of moisture to the iron ore raw material.
Here, it is indispensable to dry the conditioned iron ore raw material in order to obtain the conditioned iron ore raw material having a moisture content of 0% by mass (crystal water is not included in the moisture). However, the drying process until the water content reaches 0% by mass requires a long time and a special drying device, and it is not practical when the conditioned iron ore material is a granulated material. When is in powder form, it can be realized by a simple drying process.

On the other hand, when the moisture content of the conditioned iron ore raw material exceeds 3% by mass (less than the moisture content of the iron ore raw material), a large amount of conditioned iron ore raw material is required to reduce the moisture content of the iron ore raw material.
In addition, when producing the conditioned iron ore raw material by drying, it is preferable in terms of thermal economy to use a combustion exhaust gas containing water vapor present in an iron mill as a drying gas. In this method, moisture is 3% by mass or less. If it is a grade, it can be easily dried.
Accordingly, the moisture content of the conditioned iron ore raw material is preferably 0 or more than 0 and 3% by mass or less, but more preferably 2% by mass.

Moreover, when increasing the moisture content of an iron ore raw material, it is good to add the humidity control iron ore raw material which contains 7 mass% or more and 12 mass% or less of water to an iron ore raw material.
Since the iron ore raw material may have a moisture content of about 3% by mass when dry weathering continues, for example, to obtain an iron ore material having a moisture content of about 6 to 10% by mass, a conditioned iron ore material It is desirable that the moisture content of is 7% by mass or more.
On the other hand, if the upper limit of the moisture content exceeds 12% by mass, the conditioned iron ore raw material adheres to the structure, making it difficult to handle.
Therefore, the water content of the humidity iron Ishihara charge is preferably 12 wt% 7 wt% or more or less, 8 wt% the lower limit, it is more preferable to set the upper limit 11% by mass.

Moreover, when increasing the water content of the iron ore raw material, water can be added to the iron ore raw material.
When water is added to the iron ore raw material in advance to increase the water content, it is necessary to carry out before the step of granulating. In addition, the process of performing a granulation process means the process of including a granulator and a kneader, when performing the process by a kneader before a granulator or a granulator.
In the step of performing the granulation treatment, when moisture is added, the moisture for granulation is added together with the binder in a state where the contained moisture does not wet the particle surface. For this reason, as shown in FIG. 2B, the moisture content does not become an appropriate state.
Therefore, in this case, it is preferable to secure a time for the iron ore raw material to get wet, for example, at least 5 minutes or more, preferably 5 minutes or more and 30 minutes or less, more preferably 30 minutes or more, It is preferable to pulverize (see FIG. 1) the iron ore raw material to which water has been added before granulating the iron ore raw material after the addition, because wetting of the contained water on the iron ore particle surface can be promoted. In addition, when water | moisture content is added to the iron ore raw material on a belt conveyor whose lamination | stacking thickness is 150 mm or less, since water becomes easy to osmose | permeate the whole iron ore raw material, it is easy to promote wetting. Therefore, the time for the iron ore raw material to get wet may be secured for 2 minutes or longer, preferably 15 minutes or longer.

After controlling the moisture content of the iron ore raw material within the above-described predetermined range by the above-described method, as shown in FIG. 1, the granulation treatment is performed by adding the moisture for granulation together with the binder described above to the iron ore raw material. . The binder is added to the iron ore raw material after being mixed with part or all of the granulating moisture. In addition, after adjusting the moisture content within a predetermined range, it takes at least 2 minutes to add the binder and the moisture for granulation.
In this granulation process, the iron ore raw material is kneaded by a kneading machine (for example, a Redige mixer) and then granulated by a granulating machine (for example, a drum mixer) to obtain pellets having an average particle diameter of 3 mm. To manufacture.
Thus, by setting the average particle size of the pellets to 3 mm or more (preferably 5 mm or more), the air permeability in the sintering machine can be maintained in a good state.

The average particle size of the pellets was determined by the following procedure.
The granulated product after the granulation treatment is dried in circulating air at 150 ° C. for 1 hour, and about 2 kg of the granulated product, 10.0 mm, 8.0 mm, 6.7 mm, 4.75 mm, 2.8 mm, 2. Sieving was performed with 0 mm and 1.0 mm meshes. Then, the weight ratio between each sieve and the sieve under 1.0 mm is obtained, and the representative diameter of each particle size section is 12.0 mm, 9.0 mm, 7.35 mm, 5.73 mm, 3.78 mm, 2. The thickness was 4 mm, 1.5 mm, and 0.7 mm, and this was obtained by load average in terms of weight ratio.
The sieving procedure other than the procedure described above was performed according to the procedure described in JIS M 8706.

After producing the pellets by the above method, it is preferable to dry the pellets with a dryer and then supply the pellets to the sintering machine. However, the pellets may be supplied to the sintering machine without drying with a dryer. Good.
In addition, although the granulated material is manufactured so that it may become an average particle diameter of 3 mm or more by the granulation process, the granulated material which is not granulated by this particle size is included in part. Therefore, the granulated product after the granulation treatment may be screened and sorted (particle size sorting) by, for example, a sieving device. At this time, the granulated material under the sieve, that is, the particle size is small (eg, less than 3 mm) No granulated product is required.
Therefore, this granulated product is used as a part or all of the humidity-controlled iron ore raw material added to the iron ore raw material before the granulation treatment. This is because the granulated material is suitable for use as a conditioned iron ore raw material from the viewpoint of effective utilization of the raw material because the composition and particle size composition thereof are not different from the iron ore raw material before granulation. .

In addition, the granulated material used as this moisture-control iron ore raw material may be either before the drying treatment or after the drying treatment.
Here, the granulated product after the drying treatment is preferable because it can contribute to the improvement of pellet strength.
Further, in the drying treatment of the granulated product after the granulation treatment, the moisture content can be reduced to 3% by mass or less by the degree of drying using the combustion exhaust gas as a hot air source. For this reason, it is suitable to use the granulated material after a drying process as a moisture-control iron ore raw material at the time of reducing the moisture content of an iron ore raw material.
Furthermore, since the dried iron ore raw material is stable at a moisture content of 3% by mass or less, it is easy to adjust the moisture content after the addition of moisture. It is also suitable for use as a humidity-controlling iron ore raw material when increasing the ratio.

In addition, it is preferable to add the above-described humidity-controlling iron ore raw material to the iron ore raw material before adding the moisture for granulation, and to pulverize it together with this iron ore raw material. Thereby, an iron ore raw material and a humidity-control iron ore raw material mix evenly, and it can suppress uneven distribution of a content moisture.
Further, when the granulated product is subjected to a drying process (for example, hot air), fine powder is scattered, so that it is preferable to perform the drying process while collecting dust in view of environmental measures.
And this collect | recovered dry dust collection powder is used for a part or all of humidity-control iron ore raw material. This dry dust-collected powder is a fine powder and has a moisture content of 0 or more than 0 and about 3% by mass or less. Therefore, for the same reason as the granulated product of the fine powder after the drying treatment, the humidity-controlled iron ore It is preferable to use it as a raw material.

Next, examples carried out for confirming the effects of the present invention will be described.
First, the results of testing the effect of the particle size of the iron ore raw material particles on the strength of the granulated product will be described with reference to FIGS. 5 (A) and 5 (B).
In this test, a dispersant was used for the binder, the moisture content (R1) was 7.0% by mass, the granulation moisture rate (R2) was 2.5% by mass, and the dispersant concentration was 0.2%. The granulated material was manufactured using the iron ore raw material which made it the mass% and performed the drying process on the conditions of 150 degreeC x 1 hour.
In addition, since the original particle size distribution of the iron ore raw material was 30% by mass for 500 μm under and 2% by mass for 22 μm under, the particle size was adjusted by appropriately adding the iron ore raw material of 22 μm under and 500 μm.

As shown in FIG. 5 (A), when the proportion of particles under 22 μm is fixed to 5% by mass and the proportion of particles under 500 μm is changed, the proportion of particles under 500 μm is 40% by mass or more, It was confirmed that the strength of the granulated product was the appropriate strength standard, that is, 20 N or more.
In addition, as shown in FIG. 5B, when the ratio of particles under 500 μm is fixed to 40% by mass and the ratio of particles under 22 μm is changed, the ratio of particles under 22 μm is 40% by mass or more. Thus, it was confirmed that the strength of the granulated product was 20 N or more, which is an appropriate strength.
From the above, it was confirmed that a granulated product having an appropriate strength can be produced by using an iron ore raw material containing fine powder having a 500 μm under 40 mass% or more and a 22 μm under 5 mass% or more.

Next, the results of examining the influence of the average particle size of pellets produced by granulating iron ore raw materials on the production rate of sintered ore will be described with reference to FIG. The production rate on the vertical axis in FIG. 6 is a numerical value obtained by indexing the productivity (ton / day / m ² ) of only the pseudo particles as 100, and this productivity is a sintering machine per day. This means the production amount of the sintering machine per unit area of the pallet. In addition, the average particle size “none” of the pellets shown in FIG. 6 means that all of the granulated product (100% by mass) is composed of pseudo particles.
In this test, 50 kg of a granulated product having a pseudo particle (average particle size of 3.0 mm) of 79% by mass and a pellet of 21% by mass was charged in a pan, the layer thickness was 600 mm, and the suction negative pressure below the pan was set. It was carried out by a pan firing test made constant at 1000 mmAq.
As is apparent from FIG. 6, it was confirmed that the production rate at least higher than the current level can be achieved by setting the average particle size of the pellets to 3 mm or more.

Next, an example on the premise that the moisture content of the iron ore raw material is increased will be described with reference to FIG.
In FIG. 7, an iron ore raw material containing 40% by mass of 500 μm under and 5% by mass of 22 μm under is used, and this iron ore raw material is granulated by a kneading machine and then granulated by a drum mixer. The drying process was performed under the conditions of 105 ° C. × 1 hour to produce pellets. Here, a dispersant (concentration: 0.2% by mass) is used for the binder, and the water content ratio (R1) is 7% by mass (from 5% by mass to 7% by mass by addition of moisture or conditioned iron ore raw material). ), The ratio of moisture for granulation (R2) was adjusted to 2.5% by mass. Moreover, the granulated material (average particle diameter: 5 mm) and the dry dust collection powder (average particle diameter: 1 mm under) were used for the humidity control iron ore raw material (also called humidity control raw material).

Comparative Example 1 is a conventional method in which the content of water is increased with a kneader (water is added directly to the iron ore raw material). In this case, the strength of the granulated product is about 7N, and the appropriate strength 20N described above is increased. It was below. Hereinafter, Examples 1 to 8 will be described on the basis of the degree of migration of moisture contained in Comparative Example 1 and moisture adjustment accuracy.

Examples 1 and 2 are the results of adding water directly to the iron ore raw material.
In this Example 1, moisture is added to the iron ore raw material that has not been processed by the pulverizer before the granulation treatment, and the contained moisture is adjusted within an appropriate amount range. The crossing degree was better than Comparative Example 1 (Δ). However, since moisture was added directly to the iron ore raw material, the adjustment accuracy of the contained moisture was similar to that of Comparative Example 1 (no improvement).
As a result, the strength of the granulated product was better than that of the comparative example, but was 20N which is an appropriate strength.
Further, in Example 2, since the iron ore raw material to which water was directly added was processed by the pulverizer, the water was well mixed with the iron ore raw material, and the degree of migration of the contained water was better than in Example 1. There was (○). In addition, since Example 2 also added water directly to the iron ore raw material as in Example 1, the adjustment accuracy of the contained water was about the same as that of Comparative Example 1 (no improvement).
As a result, the strength of the granulated product could be improved to about 29N.

Examples 3 and 4 are the results of adding undried granulated material (collected at the position of arrow C in FIG. 7) to the iron ore raw material as a conditioned iron ore raw material.
In Example 3, since the undried granulated product was added to the iron ore raw material treated with the pulverizer before the granulation treatment, and the contained moisture was adjusted within the appropriate amount range, the contained moisture Although the degree of crossing was better than that of Example 1, it could not be improved to a preferred level (Δ to ○).
The moisture content is adjusted by adding the undried granulated material to the iron ore raw material, and the moisture content of the granulated material is generally known. (△).
As a result, the strength of the granulated product was such that it could be slightly improved as compared with Example 1.
In Example 4, since the iron ore raw material to which the undried granulated material was added was processed by a pulverizer, the granulated material was well mixed with the iron ore raw material, and the degree of migration of the contained water was in Example 3. (○). In addition, since Example 4 is also adjusting the moisture content by adding an undried granulated product whose moisture is generally known, the adjustment accuracy is about the same as Example 3. (△).
As a result, the strength of the granulated product was such that it could be slightly improved as compared with Example 2.

Examples 5 and 6 are the results of adding dried granulated material (collected at the position of arrow E in FIG. 7) to the iron ore raw material as a conditioned iron ore raw material.
In Example 5, since the granulated product dried before granulation treatment was added to the iron ore raw material treated with the pulverizer and the contained water content was adjusted within the appropriate amount range, Although the degree of crossing was better than Example 3, it could not be improved to a preferred level (Δ to ○).
In addition, the moisture content can be adjusted to a sufficient level by using a dried granulated product whose moisture content is known and adding water to the granulated product. (○).
As a result, the strength of the granulated product was such that it could be slightly improved as compared with Example 3.
In Example 6, since the iron ore raw material to which the dried granulated product was added was processed by a pulverizer, the granulated product was well mixed with the iron ore raw material, and the degree of water content transfer was higher than that of Example 5. Was also good (◯). In Example 6, as in Example 5, the moisture content was adjusted by adding a dried granulated product whose moisture content was known, so the adjustment accuracy was about the same as in Example 5. (○).
As a result, the strength of the granulated product could be improved to about 37N.

Examples 7 and 8 are the results of adding dry dust-collected powder (collected at the position of arrow D in FIG. 7) to the iron ore raw material as a humidity-controlled iron ore raw material.
Since this Example 7 adds the dry dust collection powder which is a fine powder before performing granulation processing to the iron ore raw material processed with the grinder, and adjusts the moisture content in the proper amount range, The dust collection powder was well mixed with the iron ore raw material, and the degree of migration of the contained water was better than that of Example 5 (◯). In addition, the moisture content can be adjusted to a sufficient level by using dry dust collected with known moisture content in the granulated product and adding water to this. ○).
As a result, the strength of the granulated product was similar to that in Example 6.
In Example 8, since the iron ore raw material to which the dry dust collecting powder, which is a fine powder, is added, is processed by a pulverizer, the dry dust collecting powder is well mixed with the iron ore raw material, and the extent of moisture content is good. (○). In Example 8, as in Example 7, the moisture content was adjusted by adding dry dust collection powder having a known moisture content, so that the adjustment accuracy was similar to that in Example 7. (○).
As a result, the strength of the granulated product could be improved to about 40N.

Next, an example premised on reducing the water content of the iron ore raw material will be described with reference to FIG.
Also in FIG. 8, an iron ore raw material containing 40% by mass of 500 μm under and 5% by mass of 22 μm under is used, and this iron ore raw material is granulated by a kneading machine and then granulated by a drum mixer. The drying process was performed under the conditions of 105 ° C. × 1 hour to produce pellets. Here, a dispersant (concentration: 0.2% by mass) is used for the binder, and the water content ratio (R1) is 7% by mass (from 9% by mass to 7% by mass by adding humidity-controlling iron ore raw material) The proportion of moisture for granulation (R2) was adjusted to 2.5% by mass. Moreover, the dried granulated material (average particle diameter: 3 mm, 5 mm, 10 mm) and the dry dust collection powder (average particle diameter: 1 mm under) were used for the humidity control iron ore raw material (also referred to as humidity control raw material).

Comparative Example 2 is a conventional method in which the ratio of moisture content is reduced with a kneader (added dried granulated material to the iron ore raw material as a conditioned iron ore raw material). It was far below the appropriate strength of 20N. Hereinafter, Examples 9 to 12 will be described on the basis of the degree of migration of moisture contained in Comparative Example 2 and moisture adjustment accuracy.

Examples 9 and 10 are the results of adding the dried granulated material (collected at the position of arrow E in FIG. 8) to the iron ore raw material as the conditioned iron ore raw material.
In this Example 9, since the granulated material dried before the granulation treatment is added to the iron ore raw material treated with the pulverizer and the contained water content is adjusted within an appropriate amount range, this granulation is performed. The material absorbs the moisture contained around the granulated material. However, since the granulated material does not spread evenly over the entire iron ore raw material, it does not absorb the moisture contained from the entire iron ore raw material, and the extent of the moisture content was better than Comparative Example 2. However, it could not be improved to a desirable level (Δ).
Moreover, since adjustment of the moisture content uses a dry granulated material whose moisture content of the granulated material is known, the accuracy could be increased to a sufficient level (◯).
In addition, since the number of granulated materials increases by making the particle size of the dried granulated material small (average particle size: 3 mm) than that having a large particle size (average particle size: 10 mm), It became easy to reach the entire iron ore raw material, and the strength of the granulated material could be improved from 20N to about 24N.
In Example 10, since the iron ore raw material to which the dried granulated product (average particle size: 5 mm) was added was processed with a pulverizer, the granulated product tends to be mixed well with the iron ore raw material. The degree of moisture migration was better than Example 9 (◯). In Example 10, as in Example 9, the moisture content was adjusted by adding a dried granulated product whose moisture content was known, so the adjustment accuracy was about the same as in Example 9. (○).
As a result, the strength of the granulated product could be improved to about 37N.

Examples 11 and 12 are the results of adding dry dust-collected powder (collected at the position of arrow D in FIG. 8) to the iron ore raw material as a conditioned iron ore raw material.
This Example 11 adds dry dust-collecting powder that is fine powder to the iron ore raw material processed by the pulverizer before the granulation treatment, and adjusts the contained water content within an appropriate amount range. The dust collection powder was well mixed with the iron ore raw material, and the degree of migration of the contained water was better than that in Example 9 (◯). Moreover, since adjustment of the moisture content uses dry dust collecting powder whose moisture content of the granulated material is known, the accuracy could be increased to a sufficient level (◯).
As a result, the strength of the granulated product was almost the same as in Example 10.
In Example 12, since the iron ore raw material to which the dry dust collecting powder, which is fine powder, was added, was processed by a pulverizer, the dry dust collecting powder was well mixed with the iron ore raw material, and the extent of moisture content was good. (○). In Example 12, as in Example 11, the moisture content was adjusted by adding dry dust-collecting powder whose moisture content was known, so that the adjustment accuracy was comparable to that in Example 11. (○).
As a result, the strength of the granulated product could be improved to about 40N.

In addition, about FIG. 7, FIG. 8 shown above, although the case where a dispersing agent is used as a binder is demonstrated, the same improvement effect is acquired also when an adhesive binder or quicklime is used as a binder. ing.
From the above, by granulating an inferior iron ore raw material containing a lot of fine powder by applying the present invention, it is assumed that there is a maximum of about 60% by mass of iron ore raw material having an average particle size over 500 μm, It was confirmed that high-strength pellets can be produced by overcoming the moisture absorption effect of the iron ore raw material and applying more precise control of the water content.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where a granulation method of an iron ore raw material containing fine powder of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the present invention.
In the above embodiment, the iron ore raw material carried from the mining mountain can be used after sieving. In the iron ore raw material to be granulated, the iron ore raw material having a particle size of 500 μm or less and the particle size are used. However, there is a case where either one or both of the iron ore raw materials having a thickness of 22 μm or less are small. In this case, it is preferable to add fine powder having the above-mentioned particle size separately. Here, the fine powder added separately is not particularly limited as long as it is a fine particle having the above-mentioned particle diameter, but for example, it is generated in limestone (calcium carbonate), kaolin clay, bentonite, and ironworks. Among inorganic substances such as dust, silica fume, fly ash, anhydrous gypsum, and colloidal silica, the use of any one kind or two or more kinds of fine particles can increase the strength during and after the sintering of the iron ore raw material. Among them, calcium carbonate, kaolin clay, and colloidal silica are particularly preferable because they can further improve the productivity of the sintering machine.

It is explanatory drawing of the granulation method of the iron ore raw material containing the fine powder which concerns on one embodiment of this invention. (A)-(C) is explanatory drawing which shows the wet condition of the water | moisture content in the iron ore particle | grains which respectively comprise an iron ore raw material. (A)-(C) is explanatory drawing which shows the granulation mechanism of the iron ore raw material at the time of using a dispersing agent as a binder, respectively. It is explanatory drawing shown about the influence which the kind of binder and the moisture content of an iron ore raw material have on pellet strength. (A), (B) is explanatory drawing shown about the influence which the particle size of the particle | grains of an iron ore raw material has on the intensity | strength of a granulated material, respectively. It is explanatory drawing shown about the influence which the average particle diameter of the pellet manufactured by granulating an iron ore raw material has on the production rate of a sintered ore. It is explanatory drawing of the Example presupposed to increase the moisture content of an iron ore raw material. It is explanatory drawing of the Example predicated on reducing the moisture content of an iron ore raw material.

Claims (12)

After controlling the moisture content of the iron ore raw material containing fine powder in which the 500 μm under is 40% by mass or more and the 22 μm under is 5% by mass or more within the predetermined range, the iron ore raw material is mixed with the moisture for granulation together with the binder. It is a method of adding and granulating to produce pellets having an average particle size of 3 mm or more,
The binder is a dispersant, and the predetermined amount range is 5.5% by mass or more and 8.5% by mass or less in terms of moisture of the iron ore raw material after adding the dispersant and the moisture for granulation. The dispersant is mixed with a part or all of the granulating water, and the amount of the dispersant is 0.001% by mass to 1% by mass with respect to the iron ore raw material amount. A method for granulating iron ore raw materials containing iron. After controlling the moisture content of the iron ore raw material containing fine powder in which the 500 μm under is 40% by mass or more and the 22 μm under is 5% by mass or more within the predetermined range, the iron ore raw material is mixed with the moisture for granulation together with the binder. It is a method of adding and granulating to produce pellets having an average particle size of 3 mm or more,
The binder is an adhesive binder, and the predetermined amount range is 4.0% by mass or more and 8.0% by mass or less in terms of moisture of the iron ore raw material after adding the adhesive binder and the granulating moisture. The adhesive binder is mixed with a part or all of the granulating moisture, and the amount of the adhesive binder is 0.1% by mass or more and 5% by mass or less based on the amount of the iron ore raw material. A method for granulating iron ore raw material containing fine powder. After controlling the moisture content of the iron ore raw material containing fine powder in which the 500 μm under is 40% by mass or more and the 22 μm under is 5% by mass or more within the predetermined range, the iron ore raw material is mixed with the moisture for granulation together with the binder. It is a method of adding and granulating to produce pellets having an average particle size of 3 mm or more,
The binder is quick lime, and the predetermined amount range is 1.0% by mass or more and 9.0% by mass or less in terms of moisture of the iron ore raw material after adding the quick lime and the moisture for granulation, The granulation method of the iron ore raw material containing the fine powder characterized by the amount of quicklime having been 0.1 mass% or more and 2 mass% or less with respect to the said iron ore raw material amount. In the granulation method of the iron Ishihara fees including fines according to any one of claims 1 to 3, the water below 3 wt% greater than 0 or 0 to the iron ore raw material before addition of the granulating water A granulation method of an iron ore raw material containing fine powder, wherein the moisture content of the iron ore raw material is controlled to be within the predetermined range by adding the containing moist iron ore raw material. In the granulation method of the iron Ishihara fees including fines according to claim 1, comprising water of 7 wt% or more and 12 mass% or less in the iron ore raw material before addition of the granulating water A method of granulating an iron ore raw material containing fine powder, wherein the moisture content of the iron ore raw material is controlled within the predetermined amount range by adding a conditioned iron ore raw material. In the granulation method of the iron Ishihara fees including fines according to any one of claims 1 to 3, by adding water to the iron ore raw material before addition of the granulating water, the iron ore raw material A method for granulating an iron ore raw material containing fine powder, characterized in that the moisture content of the iron is controlled within the predetermined amount range . In the granulation method of the iron ore raw material containing the fine powder according to claim 6, the iron ore raw material to which the water is added is pulverized after the water is added and before the iron ore raw material is granulated. A method for granulating a raw iron ore material containing fine powder. In the granulation method of the iron ore raw material containing the fine powder according to any one of claims 4 and 5, the moist iron ore raw material is a sieve under the sieving and sorting of the iron ore raw material after the granulation process. A method for granulating an iron ore raw material containing fine powder, comprising an iron ore raw material. In the granulation method of the iron ore raw material containing the fine powder according to any one of claims 4, 5, and 8, the moisturized iron ore raw material is further subjected to a dry treatment of the iron ore raw material after the granulation treatment. A method for granulating an iron ore raw material containing fine powder, comprising an iron ore raw material. The method of granulating an iron ore raw material containing fine powder according to claim 9, wherein the humidity-controlled iron ore raw material is added to the iron ore raw material and pulverized together with the iron ore raw material before adding the moisture for granulation. A method for granulating an iron ore raw material containing fine powder. In the granulation method of the iron ore raw material containing the fine powder of any one of Claims 4, 5, and 8-10, the said humidity-control iron ore raw material further dries the said iron ore raw material after a granulation process. A method for granulating an iron ore raw material containing a fine powder, characterized by having a dry dust collection powder generated when it is treated. In the granulation method of the iron ore raw material containing the fine powder according to any one of claims 1 to 11, the iron ore raw material is a blended iron ore in which two or more types of iron ore raw materials are mixed. A method for granulating iron ore raw materials containing fine powder.

Images