JP4786441B2 - Pretreatment method of sintering raw material - Google Patents

Description

The present invention relates to a pretreatment method for a sintering raw material.

In recent years, the supply amount of iron ore such as hematite, which has been conventionally used in sintering machines, has decreased, and the supply amount of iron ore having a high crystal water content (3 mass% or more) has increased. This iron ore with a high content of water of crystallization contains more fine powder than the iron ore that has been used in the past, so if this iron ore is charged into the sintering machine without pretreatment, the air permeability of the sintering machine will be reduced. The sinter with good quality cannot be produced with good productivity. For this reason, it is necessary to granulate iron ore before charging it into the sintering machine, but it has the disadvantage that it is poor in wettability with water and has low granulation properties compared to iron ore that has been used in the past. Therefore, a technique for granulating this has become necessary.
Therefore, for example, Patent Document 1 discloses a technique of pulverizing iron ore and limestone so that 250 μm or less is 80% by weight or more and producing a granulated product in the presence of water. Patent Document 2 discloses a technique for producing a granulated product of fine ore through two granulations.

Japanese Patent Laid-Open No. 4-80327 JP-A-53-123303

However, the conventional sintering raw material pretreatment method still has the following problems to be solved.
The method disclosed in Patent Document 1 requires time and labor for pulverizing all limestone serving as a binder, is not economical because of an increase in production cost due to pulverization, and the productivity of the granulated product is very poor. . Further, if the pulverized particle size of 250 μm or less is merely 80% by weight or more, the strength of the granulated product produced using this, that is, the P-type granulated product cannot be increased to the intended strength. When transporting particles via multiple belt conveyors, the granulated material is pulverized at the time of transit , and this is inserted into the sintering machine to impede the air permeability of the sintering machine. There was a risk that the granulated material collapsed in the pallet and hindered air permeability .
Moreover, the method disclosed in Patent Document 2 may improve the strength of the granulated product. However, for example, in the case of producing a granulated product in which fine powder is adhered to coarse particles serving as core particles, that is, an S-shaped granulated product, the thickness of fine powder deposited cannot be controlled. For this reason, if the adhesion thickness is thick, coke is buried inside the granulated material, making it difficult to produce sintered ore with the desired quality, leading to a decrease in yield of sintered ore, Productivity is impaired.

The present invention has been made in view of such circumstances, and can produce pellets having a higher granulation property and strength than the conventional pellets, which can cope with iron ore raw materials containing a larger amount of fine powder than before, and has good quality. It aims at providing the pre-processing method of the sintering raw material which can manufacture the sintered ore provided with.

The sintering raw material pretreatment method according to the first invention that meets the above-mentioned object includes at least part of iron ore having a crystal water content of 3 mass% or more, and a plurality of pellets granulated in the presence of moisture . before charging via belt conveyor and its transit unit in the sintering machine, the temperature of the pellets were dried so that 250 ° C. or less 40 ° C. or higher to suppress the decomposition of water of crystallization.
In the pretreatment method of the sintering raw material according to the first invention, examples of the iron ore having a crystal water content of 3 mass% or more include maramamba ore, pisolite ore, and high phosphorus block man ore. Thus, in the granulated product of iron ore having a high crystallization water content (3 mass% or more), when the crystallization water is decomposed, the pellets are disintegrated and powdered.
Moreover, the pre-processing method of the sintering raw material which concerns on 2nd invention WHEREIN: In the pre-processing method of the sintering raw material which concerns on 1st invention, let the drying temperature of the said pellet be below the decomposition temperature of crystallization water.
For this reason, in the pretreatment method of the sintering raw materials according to the first and second inventions, the lower limit of the drying temperature is 40 ° C., preferably 100 ° C., the upper limit is 250 ° C., preferably 240 ° C., and further there is crystallization water. The theoretical temperature for decomposition is preferably 239 ° C.

In the pretreatment method of the sintering raw material according to the first and second inventions, the drying temperature is set to 40 ° C. or more and 250 ° C. or less, so that the decomposition of the crystal water is suppressed and further prevented, and the pellets collapse, Can be suppressed and further prevented.

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 an explanatory view of a sintering raw material pretreatment method according to an embodiment of the present invention, and FIG. 2 is an explanatory view showing the influence of the fine powder adhesion thickness of the S-type granulated product on the coke combustion index. FIG. 3 is an explanatory diagram showing the crushing strength required for suppressing the collapse of the P-type granulated product, and FIG. 4 is an explanatory diagram showing the influence of the production conditions of the P-type granulated product on the crushing strength.

As shown in FIG. 1, the sintering raw material pretreatment method according to one embodiment of the present invention includes three types of iron ore containing coarse grains and fine powder, that is, a psolite ore, a maramamba ore, and a high phosphorus block. S-type granulated product (granulated product S) made of man ore as raw material and fine particles adhering to coarse particles as core particles, and P-type granulated product (granulated product P) granulated mainly with fine powders It is a method of manufacturing. In addition, iron ore substantially consisting only of fine powder, that is, kneaded dust generated in the steel mill, pellet feed (ore type: MBR-PF), and other iron ores are further added to the raw material. This will be described in detail below.

Maramamba ore, pisolite ore, and high phosphorus block man ore are also called limonite (Fe ₂ O ₃ · nH ₂ O), and are iron ores with a crystal water content of 3 mass% or more. In this embodiment, it has a coarse particle of about 8 mm) to a fine powder of 250 μm or less.
S-type granulation is produced using this pisolite ore, fine coke, other iron ores, and limestone, and P-type granulation using maramamba ore, high phosphorus blockman ore, kneaded dust, and pellet feed Manufacturing things.

First, the manufacturing method of S type granulated material is demonstrated.
As shown in FIG. 1, pisolite ore containing coarse particles and fine powder is sieved by a sieve sorter 10. In addition, in this Embodiment, although the thing of 3 mm was used as a sieve mesh of the sieve sorter 10, it is not limited to this.
Since the iron ore on the sieved sieve is coarse, it is used as a core particle as it is without being treated. On the other hand, the iron ore under the sieve is charged into the Eirich mixer 11 and is kneaded and granulated with a binder such as limestone.

The above-mentioned kneaded granulated material is charged into an S-type drum mixer (an example of a first granulating device) 12 together with powdered coke, other iron ores, and limestone, and powdered coke, etc. around the core particles Iron ore and fine powder (for example, 250 μm or less) contained in limestone are adhered. Thereby, the S type granulated product in which the average thickness of the fine powder adhered to the periphery of the core particle is 50 to 300 μm is manufactured. At the time of production of the S-type granulated product, some of the particles having a particle size exceeding 250 μm contained in the powdered coke, other iron ores, and limestone, together with the S-type granulated product, are drum mixers for S type. 12 is discharged from the inside.

Here, the reason why the average fine powder adhesion thickness of the S-shaped granule is defined in the range of 50 to 300 μm will be described with reference to FIG.
The average fine powder adhesion thickness, which is the horizontal axis in FIG. 2, was calculated by the following procedure using the produced S-shaped granulated product.
(1) First, the target raw material is completely separated into fine particles, coarse particles, etc. by washing with water, etc., and sieved under the sieve order of 5 mm, 2 mm, 1 mm, 0.5 mm, and 0.25 mm. Then, the weight ratio of each particle size section was obtained (weight g of each particle size section when the whole is 100 g).

(2) The representative particle diameter (7.5 mm, 3.5 mm, and 1.5 mm, respectively) of each section of 5 mm or more, less than 5 mm, 2 mm or more, and less than 2 mm, or 1 mm or more to be the core particles was determined to be 100 g as a whole. The number of core particles for each representative particle size was calculated from the weight ratio of each particle size section. At that time, the core particle density was set to 4 g / cm ³ .
(3) When distributing fine powder of 0.25 mm or less, which becomes a powder adhering to the core particles, for each core particle section, each core particle section is proportional to the core particle weight ratio of each core particle section. The weight of fines to be dispensed was determined.
(4) The adhesion thickness of each core particle was calculated from the number of core representative particle diameters calculated in (2) and the fine powder weight distributed and calculated in (3). At that time, the bulk density of the adhered powder layer was set to 2 g / cm ³ .
(5) The weight of the adhered powder in each core particle section was weighted and averaged with the weight ratio of each particle section to obtain the fine powder deposited average thickness.

The coke combustion index on the vertical axis in FIG. 2 corresponds to the yield of sintered ore obtained by sintering the S-type granulated product, and as the coke combustion index increases, Yield is also improved.
FIG. 2 shows the relationship between the fine powder adhesion thickness (μm) and the coke combustion index in a test in which raw materials having various particle size distributions were granulated and then sintered in a pan test.
As shown in FIG. 2, the coke combustion index increased with increasing thickness until the fine powder adhesion thickness reached 100 μm, and thereafter decreased with increasing thickness.
Considering that the above does not affect the yield deterioration of the sintered ore, the average fine powder adhesion thickness is defined as 50 to 300 μm, preferably the upper limit is 250 μm, more desirably 220 μm. .

Based on the above knowledge, there are three types of S that have a fine powder adhesion average thickness of 204 μm (current situation), a thinner adhesion thickness of 88 μm, and a thicker adhesion thickness of 327 μm. Mold granulated materials were prepared, and each S-shaped granulated material was charged into a sintering machine, and the influence on the yield of sintered ore was investigated.
In addition, since each S type granulated material is manufactured under a fixed amount of iron ore, the 327 μm S type granulated material (only pulverized) is obtained by pulverizing iron ore with an insufficient amount of fine powder. It was manufactured by adhering to the periphery of the core particles and charged into a sintering machine. The 88 μm S-type granulated product was produced by granulating the remaining fine powder not used in the S-type granulated product. The mold is granulated (pelletized) and charged into the sintering machine. Here, the survey result of the 88 μm S-type granulated product is not only the result of the S-type granulated product, but the blending amount of the P-type granulated product is small (for example, S-type granulated product and P-type granulated product 20-30 mass% of the total amount of the product), and since powder coke as a heat source is not contained in the P-type granulated product, the obtained result can substantially correspond to the result of the S-type granulated product Conceivable.
As a result of the above investigation, the yield of sintered ore along the coke combustion index of the result of the pan test in FIG. 2 was obtained.

Next, the manufacturing method of P type granulated material is demonstrated.
As shown in FIG. 1, the maramamba ore and the high phosphorus block man ore containing coarse particles and fine powder are sieved by a sieve sorter 13. In addition, the sieve mesh of the sieve sorter 13 is set in a range of 0.5 to 10 mm (3 mm in the present embodiment). The iron ore under the sieve that has been sieved by the sieve sorter 13 is pulverized by a pulverizer 15 and charged into a mixer 17 together with kneaded dust and pellet feed (MBR-PF) and mixed. In addition, the sieve sorter 13 and the pulverizer 15 each constitute a pretreatment device.
At this time, subsequent processing is performed according to the pulverized particle size distribution of the iron ore used to produce the P-type granulated product.

When sieving iron ore that is the raw material of P-type granulated material is pulverized and sized so that 500 μm under 90% or more and 22 μm under 80% by mass, P-type drum mixer (second granulation An example of an apparatus) 18 is charged, granulated using water (for example, 5 to 15 mass% in an external portion), and then sieved by a sieve sorter 19. In addition, when sieving iron ore that is a raw material for P-type granulated material is pulverized and sized so that the 500 μm under is 80 mass% or more and the 22 μm under is more than 70 mass% and not more than 80 mass%, the P type drum After being charged into the mixer 18 and granulated using water (for example, 5 to 15 mass% as an external component), the mixture is sieved with a sieve sorter 19 and further dried with a dryer 20.
And when sieving iron ore that is the raw material of P-type granulated material, and sized so that 500 μm under is 40 mass% or more and 22 μm under is 5 mass% to 70 mass%, P type drum mixer 18, for example, an organic binder such as pulp waste liquid and corn starch (for example, preferably 0.01 to 3% by mass, more preferably 0.1 to 3% by mass) and After granulation using water (for example, 5 to 15 mass% as an external component), the mixture is sieved with a sieve sorter 19 and further dried with a dryer 20.
In addition, drying is performed in an atmosphere set to 40 ° C. or higher and 250 ° C. or lower, for example, for about 20 to 60 minutes. Moreover, when measuring mass% of fine powder particles such as 500 μm under and 22 μm under, a laser diffraction scattering measuring instrument (MICROTRAC FRA type, measurement range: 0.1 to 700 μm manufactured by Nikkiso Co., Ltd.) was used.

Here, the reason why each of the subsequent processes is changed according to the particle size distribution of the crushed and sized iron ore will be described.
When fine powder is used as a raw material for a P-type granulated product (hereinafter also referred to as pellets), the strength (crushing strength) of the P-type granulated product is low, and it is necessary to increase this strength to an appropriate value. For this reason, if this necessary strength is defined in consideration of having a strength that does not cause any problem even if the belt conveyor (not shown) is connected five times or more (equivalent to an actual machine connection), the diameter is as shown in FIG. It turns out that the intensity | strength of 2 kgf (2kgf / 10mmphi * 1 piece) or more is required per 10 mm P-type granulated material.
Therefore, a processing method that satisfies this 2 kgf / 10 mmφ · 1 or more will be described with reference to FIG. In addition, the used raw material is what crushed 3 mm or less of maramamba ore, pellet feed, and kneaded dust.

As shown in FIG. 4, (1) pulverization treatment only, (2) pulverization treatment and drying treatment, (3) pulverization treatment, drying treatment, and binder addition treatment, (1) → (2) → The tendency of the crushing strength of the pellets to increase as (3) was obtained. The amount of water used for granulation is 10% by mass in the outer portion, the amount of binder (pulp waste liquid) added is 1% by mass in the outer portion, and drying is performed at 250 ° C. for 30 minutes, and is contained in the granulated product. The amount of water was reduced to 5 mass% with an external component. Here, when the iron ore is only pulverized, if the average particle size is 20 μm or less (500 μm under is 90 mass% or more and 22 μm under is over 80 mass%), the produced pellet is 2 kgf / 10 mmφ × 1 piece. The above conditions can be satisfied.

Further, when this granulated product is further subjected to a drying treatment, the average particle size is increased to 100 μm or less (500 μm under is 80 mass% or more and 22 μm under is more than 70 mass% and 80 mass% or less). The condition of 2 kgf / 10 mmφ · 1 or more can be satisfied.
Furthermore, when the granulated product to which the binder has been added is subjected to a drying treatment, the average particle size is further increased to 700 μm or less (500 μm under is 40 mass% or more and 22 μm under is 5 mass% or more and 70 mass% or less). The satisfied pellets can satisfy the condition of 2 kgf / 10 mmφ · 1 or more.
From the above, the above-described treatment was performed according to the pulverized particle size.

The sieve mesh of the sieve sorter 19 for sieving the granulated product granulated by the P-type drum mixer 18 is adjusted so that the granulated product having a particle size in the range of 1 to 10 mm can be sieved. Yes. The granulated product having a particle size of less than 1 mm is charged again into the mixer 17 without being processed, and the granulated product having a particle size of more than 10 mm is crushed by a crusher (not shown) and again. The particle size is adjusted by charging the mixer 17.
Thereby, as described above, the granulated product whose particle diameter is adjusted to the range of 1 to 10 mm is subjected to a drying treatment as necessary to become a P-type granulated product.

In addition, the iron ore on the sieve generated by sieving the maramamba ore and the high phosphorus block man ore with the sieve mesh set in the range of 0.5 mm to 10 mm of the sieve sorter 13 in the production of the P-type granulated product. Is not suitable as a raw material for P-type granules. As described above, if the pulverization treatment is not performed, it is difficult to ensure the strength of the manufactured P-type granulated product, and there is a relatively large pulverization load compared to the sieving iron ore. This is because a load is applied. Therefore, the iron ore on the sieve is mainly used as the core particle of the S-type granulated product without being pulverized.
Thus, the fine powder contained in the Mara Mamba ore and the high phosphorus block man ore is adjusted to a state in which the fine powder blending amount is adjusted by the mesh of the sieve sorter 13, that is, not supplied to the S-type drum mixer 12. The remainder that is not supplied to the drum mixer 12 as much as possible, that is, almost all the fine powder, is used as a raw material for the P-type drum mixer 18.

Here, according to the fine powder adhesion average thickness of the S-type granulated product, the sieve mesh of the sieve sorter 13 is changed in size, and the iron ore in the iron ore excluding the fine powder supplied to the P-type drum mixer 18 is used. By adjusting the blending amount of the coarse particles into the S-type drum mixer 12, the average fine powder adhesion thickness can be set to a target predetermined range of 50 to 300 μm.
For example, when the fine powder adhesion average thickness of the S-type granulated product increases due to the change in the particle size distribution of the iron ore used, it is supplied to the S-type drum mixer 12 using a sieve mesh close to 1 mm within a range of 1 mm or more. By increasing the amount of core particles of the S-shaped granulated product, the average fine powder adhesion thickness can be optimized. On the other hand, for example, when the fine powder adhesion average thickness of the S-type granulated material decreases due to the change in the particle size distribution of the iron ore used, the S-type supplied to the S-type drum mixer 12 using a sieve mesh close to 10 mm. By reducing the amount of core particles in the mold granulated product, the average fine powder adhesion thickness can be optimized.

Further, the sieve mesh of the sieve sorter 13 is changed in size according to the production capacity of one or both of the P-type drum mixer 18 and the pretreatment device, and the supply amount of iron ore to each device is changed. Can be controlled (changed).
For example, if there is a margin in the production capacity of each device for producing P-type granulated material due to changes in the particle size distribution of the iron ore used, the raw material for producing P-type granulated material using a sieve mesh close to 10 mm The supply amount of can be increased. On the other hand, for example, when the production capacity of each device for producing a P-type granulated product is insufficient due to a change in the particle size distribution of the iron ore to be used, a sieve mesh close to 0.5 mm is used, and the P-type granulated product is used. The amount of raw material to be manufactured can be reduced. At this time, when the iron ore under the sieve is temporarily stocked (stored) and the capacity of each device for producing the P-type granulated material is sufficient, measures such as processing the stocked iron ore should be taken. It can also be used as necessary.

Moreover, when adjusting the sieve mesh of the sieve sorter 13, intermediate particles (for example, more than 250 μm and 1 mm or less) that are difficult to become core particles contained in the iron ore on the sieve do not adhere to the S-type granulated product. It is often discharged from the S-type drum mixer 12. In addition, this intermediate particle can be used as a raw material for the P-type granulated product by pulverization or as an adhering fine powder of the S-type granulated product.
The S-type granulated product and the P-type granulated product produced by the above method are sintered without being mixed so that, for example, 70 to 80 mass% of the total amount becomes the S-type granulated product. 21 is charged to produce sintered ore.
As a result, it is possible to cope with iron ore raw materials containing a larger amount of fine powder than before, producing granulated products with improved granulation properties and strength, and producing sintered ores with good quality. it can.

As described above, the present invention has been described with reference to one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and is described in the claims. Other embodiments and modifications conceivable within the scope of the above are also included. For example, a case in which the sintering raw material pretreatment method 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 right of the present invention.
Moreover, in the said embodiment, although the case where a pisolite ore, a maramamba ore, and a high phosphorus block man ore were used as three types of iron ores containing a coarse grain and a fine powder, respectively, a coarse grain and a fine powder were respectively used. 2 or more types of iron ores may be used, for example, use of pisolite ore and maramamba ore, and other iron ores such as magnetite (Fe ₃ O ₄ ), hematite (Fe ₂ O ₃ ) Etc. can also be used. Of course, it is also possible to configure the raw materials by adding other iron sources, for example, iron sources generated in the ironworks, to these iron ores.
And in the said embodiment, when manufacturing the P-type granulated product, when the particle size after pulverization and pulverization of the fine powder is set to 90 mass% or more for 500 μm under and 80 mass% for 22 μm under, a binder is added. However, it is also possible to perform either one or both of binder addition and drying treatment as necessary. In addition, when the particle size after pulverization and pulverization of the fine powder is 80 mass% or more for 500 μm under and more than 70 mass% and not more than 80 mass% for 22 μm under, granulation is performed without adding a binder, followed by drying treatment and baking. Although it was charged into the kneading machine, it is possible to add a binder as required.

It is explanatory drawing of the pre-processing method of the sintering raw material which concerns on one embodiment of this invention. It is explanatory drawing which shows the influence of the fine powder adhesion thickness of S type granulated material which acts on a coke combustion index. It is explanatory drawing which shows the crushing intensity | strength required for the collapse suppression of P-type granulated material. It is explanatory drawing which shows the influence of the manufacturing conditions of P type granulated material which gives to crushing strength.

Explanation of symbols

10: Sieve sorter, 11: Eirich mixer, 12: S-type drum mixer (first granulator), 13: Sieve sorter, 15: Crusher, 17: Mixer, 18: P-type drum Mixer (second granulator), 19: sieve sorter, 20: dryer, 21: sintering machine

Claims (2)

Before charging pellets granulated in the presence of moisture containing iron ore with a crystallization water content of 3 mass% or more into at least a portion via a plurality of belt conveyors and their connecting parts. A pretreatment method for a sintering raw material , wherein the pellet is dried so that the temperature of the pellet is 40 ° C. or higher and 250 ° C. or lower to suppress decomposition of crystal water . 2. The pretreatment method for a sintering material according to claim 1, wherein a drying temperature of the pellet is set to be equal to or lower than a decomposition temperature of crystal water.

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