JP6887717B2 - Charcoal interior granulated particles for sinter production and sinter production method using them - Google Patents

Description

The present invention relates to a technique for producing a sinter used as a raw material for iron making in a blast furnace or the like, and specifically, a carbonaceous material interior granulated particles as a raw material for sinter used in the production of the sinter and the granulated particles thereof. It relates to the method for producing the sinter used.

Currently, the blast furnace ironmaking method mainly uses iron-containing raw materials such as iron ore and sinter as an iron source. _{Here, the sinter is a secondary material composed of a SiO 2-} containing raw material such as siliceous stone, serpentine, refined nickel slag, and a CaO-containing raw material such as limestone and fresh lime, in addition to iron ore having a particle size of 10 mm or less. An appropriate amount of water is added to a granulation raw material composed of a solid fuel (charcoal material), which is a coagulant made of raw materials, powdered coke, smokeless charcoal, etc., and mixed and granulated using a drum mixer, etc. to form pseudo-particles. After making a certain sintering raw material, the sintering raw material is charged on a pallet that circulates and moves in a sintering machine, and the carbonaceous material contained in the pseudo particles is burned and sintered, and the obtained sintered cake is obtained. It is a kind of agglomerate ore that is crushed, sized, and recovered as a product with a certain particle size or larger.

By the way, in recent years, as the above-mentioned agglomerate ore, one in which an iron source such as iron ore or dust and a charcoal material such as coke are arranged in close proximity has attracted attention. The reason is that, for example, when an iron source such as iron ore and a carbonaceous material are placed close to each other in one agglomerate ore, a reduction reaction (exothermic reaction) on the iron source side and a gasification reaction (endothermic reaction) on the carbonaceous material side are performed. ) And repeatedly occur at a high speed, so that the iron making efficiency can be improved and the temperature inside the blast furnace can be lowered.

Examples of the agglomerate ore include coal, which is a raw material in which iron-containing powder generated in the iron-making process such as blast furnace / converter dust, rolling scale, sludge, and iron ore powder, which is disclosed in Patent Document 1, is used alone or mixed. Some products are granulated by adding charcoal material such as coke and starch, mixing and kneading, and then supplying a starch solution with a granulator. However, in the agglomerate ore disclosed in Patent Document 1, since the carbonaceous material in the pellet is burned during the production of the sintered ore, the iron-containing raw material such as iron ore and the coal material are actually arranged in close proximity to each other. It's not a thing. In addition, if the particle size of iron ore or carbonaceous material is simply reduced for the purpose of close placement, the movement resistance of the gas that propagates heat becomes too large, which in turn causes a decrease in the reaction rate and a decrease in iron making efficiency. I will let you.

Therefore, some techniques have been proposed for the purpose of arranging iron ore and carbonaceous material in close proximity (see, for example, Patent Documents 2 to 5). The technology disclosed in these is basically a mixture of an iron-containing raw material such as iron ore and a charcoal material such as coke, and then hot-molded and agglomerated, or raw particles without firing. As it is, it is used as a raw material for iron making in blast furnaces and the like. However, since these agglomerates are non-fired ones composed of a homogeneous mixture or a multi-layered granulated product, their strength is insufficient and pulverization is intense. Therefore, when they are charged into a blast furnace or the like, they are dehydrated and pulverized. There is a problem that the amount of use is limited because the air permeability of the blast furnace is hindered by causing reduction powdering.

Further, as a technique for solving the problems of the techniques of Patent Documents 2 to 5, for example, in Patent Document 6, a nucleus is formed from a raw material containing 5 wt% or more of metallic iron and / or 5 wt% or more of carbon. After forming one or more outer layers containing the nucleus with a raw material containing 10 wt% or more of metallic iron and 5 wt% or less of carbon, the lumps for iron making were agglomerated by firing in an oxidizing atmosphere at 300 to 1300 ° C. Mines have been proposed. However, also in the agglomerate ore disclosed in Patent Document 6, it is essential to use metallic iron as a raw material, and there is a quantitative restriction on the raw material used, so that the amount that can be produced as an agglomerate for iron making is limited. There is a problem.

Therefore, as a technique for overcoming the above-mentioned problems of Patent Documents 1 to 6, a technique for carbonaceous interior agglomerate ore has been proposed. For example, in Patent Document 7, iron oxide having a low degree of oxidation is coated with iron oxide containing metallic iron such as iron-making dust and mill scale around a carbon core made of small coke by using a granulator. After the shell is coated and formed, it is oxidized by heating it in the air at a temperature of 200 ° C. or higher and lower than 300 ° C. for 0.5 to 5 hours, so that only the surface of the iron oxide shell is composed of iron oxide having a high degree of oxidation. A technique for obtaining a carbonaceous interior agglomerate by forming a hard thin layer, and in Patent Document 8, iron oxide powder such as iron-making dust and mill scale or iron ore powder and carbonaceous material are used as a granulator. It is mixed and granulated using it, and then the outer surface of the granulated product is coated with iron oxide powder containing metallic iron to form a low-oxidation iron oxide shell, thereby forming iron oxide powder or iron ore powder. A technique for obtaining agglomerates containing coke powder having a size of 3 mm or less in a dispersed state is disclosed.

Further, Patent Document 9 discloses a method of preparing wet pellets in which a carbonaceous material is coated with iron ore powder and a CaO-containing raw material, mixing the wet pellets with the sintering raw material, and then firing in a downward suction type sintering machine. ..

Japanese Unexamined Patent Publication No. 2001-348625 Japanese Patent No. 3502008 Japanese Patent No. 3502011 Japanese Unexamined Patent Publication No. 2005-344181 Japanese Unexamined Patent Publication No. 2002-241853 Japanese Unexamined Patent Publication No. 10-183262 Japanese Unexamined Patent Publication No. 2011-195943 Japanese Unexamined Patent Publication No. 2011-225926 Japanese Patent No. 5790966

According to the techniques disclosed in Patent Documents 7 and 8, it has an appropriate size and sufficient strength as an iron-making raw material, and the iron-containing raw material and the charcoal material are arranged close to each other, so that an iron-making reaction is likely to occur, and low-temperature reduction is performed. It is possible to obtain a carbonaceous material interior mass ore with a structure capable of However, in the above technique, if the amount of metallic iron is large, the wettability with the carbonaceous material deteriorates, so that it is difficult to form a coating of metallic iron-containing iron oxide powder on the surface of the carbonaceous material core, and an iron oxide shell having a low degree of oxidation is formed. Therefore, it is said that the production amount is limited because the production cost increases because the oxidation treatment is required after granulation, and the amount of metallic iron-containing iron oxide powder such as iron-making dust and mill scale is small. There's a problem.

Further, in the technique disclosed in Patent Document 9, there is a description that a pellet feed having a particle size of 10 to 1000 μm is used, but the word “particle size” refers to the representative diameter of each particle, or the particle group. It is ambiguous whether it refers to the arithmetic mean diameter, harmonic mean diameter, or median diameter. Further, if a concentrate fine powder having a median diameter of 100 μm or more is used, the number of contact points between the particles or the number of liquid crosslinks with water as a binder is insufficient due to the large particle size, and a wet pellet having sufficient strength is produced. It is difficult. In this case, the pellets may be worn or disintegrated due to handling such as transportation on a belt conveyor, and the air flow may be deteriorated when the pellets are charged into a sintering machine and fired, resulting in a decrease in production amount.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to minimize or without using metallic iron-containing iron oxide powder such as iron-making dust and mill scale, which generate a limited amount. When the raw material conditions for obtaining the carbonaceous interior granulated particles having sufficient strength to withstand handling such as transportation are specified, and the sintered raw material containing the granulated particles is charged into a sintering machine and fired. It is an object of the present invention to provide carbonaceous material interior granulated particles capable of producing sinter without reducing the production amount by suppressing deterioration of aeration.

As a result of diligent studies on the problems of the above-mentioned prior art, the inventors have used a raw material defined by the specific surface area of iron ore powder as a coating raw material for granulated particles in the carbon material interior. It has been found that the sinter can be produced without reducing the production amount of the sinter by suppressing the deterioration of aeration when the sinter raw material containing the granulated particles is charged into the sinter and fired. developed.

That is, the present invention is a carbonaceous material interior granulated particle for producing sinter, which has a carbonaceous material core and an outer layer in which the periphery of the carbon material core is coated with a mixed powder composed of iron ore powder and CaO source powder. The iron ore powder has a specific surface area of 1000 cm ² / g or more, and is a carbonaceous material interior granulated particle for producing sinter.

In addition, in the carbonaceous material interior granulated particles for the production of sinter according to the present invention configured as described above,
(1) The CaO source powder is a CaO-containing raw material such as quicklime, limestone, and dolomite, and the CaO content in the mixed powder is 10 mass% or less.
Is considered to be a more preferable solution.

Further, in the present invention, the carbonaceous interior granulated particles for sinter production are merged with other granulated particles for sintering to mix both granulated particles, and then the mixed granulated particles are produced. A method for producing sinter is characterized in that sinter is obtained by charging the particles into a sinter and sintering the particles.

According to the present invention, by using a raw material having a specific surface area of 1000 cm ² / g or more of iron ore powder as a coating raw material for forming an outer layer of carbonaceous interior granulated particles, a sintered raw material containing carbonaceous interior granulated particles is baked. It is possible to suppress deterioration of aeration when charging into a knot and firing, and to produce sinter without reducing the amount of sinter produced.

It is a figure for demonstrating an example of the equipment line which carries out the manufacturing method of the sinter using the carbonaceous material interior granulation particles of this invention as a sinter raw material. It is a graph which shows the relationship between the compounding ratio of the carbonaceous material interior granulation particles and the specific productivity ratio in Example 1. FIG.

FIG. 1 is a diagram for explaining an example of an equipment line for carrying out a method for producing a sinter using the carbonaceous material interior granulated particles of the present invention as a sinter raw material. A method for producing the sinter used in the present invention will be described with reference to FIG.

In the example shown in FIG. 1, coke particles as core particles of 3 mm or more, concentrate fine powder (PF) of 150 μm or less, and quicklime as a flux are charged into a pelletizer, mixed, granulated, and granulated to 8 mm or more. The size of the carbonaceous material interior granulation particles shall be. Since the above raw materials are granulated with coke particles having a large particle size as nuclei, they may be added at the same time. Further, the charging ratio of the coke particles and the PF is determined so that the thickness of the PF layer of the outer layer is 2 mm or more with respect to the coke particles to be the core particles.

Next, the carbonaceous interior granulated particles obtained as described above are mixed with ordinary sintering granulated particles (pseudo-particles) obtained by stirring the conventional raw material with a drum mixer or the like and granulating. Both granulated particles are mixed and carried into the surge hopper of the sintering machine, and charged from the surge hopper onto a pallet that circulates and moves in the sintering machine. Since the grain size of the carbonaceous material interior granulated particles is larger than that of ordinary granulated particles for sintering (pseudo-particles), the temperature at the time of sintering tends to be higher than that on the upper layer side due to segregation at the time of charging. And since it is contained in a large amount on the lower layer side, the sintering reaction can be sufficiently advanced.

As described above, since the carbonaceous material interior granulated particles (aggregate ore) of the present invention can be produced by using an actual sintering machine, they can be mass-produced at low cost.

The sinter of the present invention is produced by the above-mentioned equipment line, and the feature of the present invention is that iron ore powder and CaO surround the sinter core and the sinter core as a sinter raw material for sinter production. Carbon material interior granulation particles for sinter production, which have an outer layer coated with a mixed powder composed of the source powder, and the specific surface area of the iron ore powder is 1000 cm ² / g or more. The point is that a sintered raw material containing particles is used.

Regarding the production of carbonaceous interior granulated particles for the production of sinter of the present invention, it is conventionally known if ^{the specific surface area of the iron ore powder constituting the coating layer can be 1000 cm 2 / g or more.} A manufacturing method can be used.

In the present invention, it is preferable to use the specific surface area measured by the brain air permeation method specified in JIS R 5201 as an index showing the size of the concentrate fine powder which is a raw material of the carbonaceous interior granulated particles. This method is widely used in the cement industry and the mining industry as an index showing the degree of powdering or crushing of powdered solids, and also in the technique according to the present invention, the size of iron ore powder crushed in the process of beneficiation, that is, crushing. Since the degree is an important factor that determines the strength of the wet pellet, the specific surface area was used as an index showing the size of the raw material powder.

Furthermore, in the case of a powder having a wide particle size distribution such as crushed ore, when trying to express the size of the powder by the particle size, whether to use the arithmetic mean diameter, or the harmonic mean diameter or median diameter. The values differ greatly, and even if the particle size is the same, the particle size distribution is not always uniquely determined. In that respect, the above-mentioned specific surface area is an index that can directly quantify the degree of pulverization, and the measurement method is extremely simple.

Further, the reason why the CaO-containing raw material is blended in the raw material powder for coating the carbonaceous material is to melt the iron ore particles at a lower temperature and promote sintering. However, if the CaO content in the raw material powder exceeds 10 mass%, the coating layer is excessively melted during firing, and the shape as pellets cannot be maintained. As a result, the contained coke is exposed, burned, and disappears. In order to prevent this, the CaO content in the raw material powder is preferably 10 mass% or less.

Examples and comparative examples according to the present invention are shown below.

<Example 1: Relationship between the specific surface area and the specific productivity of iron ore powder constituting the outer layer of the carbonaceous interior granulated particles>
In this test, a sinter production test was carried out using a pot tester having a diameter of 300 mm and a height of 600 mm. Table 1 shows the test conditions. The specific surface area was measured according to the brain air permeation method specified in JIS R 5201.

For samples having different specific surface areas, one type of powder ore was crushed and the specific surface area was adjusted to a predetermined value. A coating layer was formed around the powder coke having a diameter of 5 mm using iron ore powder whose specific surface area was adjusted so as to have a thickness of 5 mm, and carbonaceous interior granulated particles were produced.

The blending amount of the carbonaceous interior granulated particles was changed in the range of 5 to 30 mass% with respect to all the raw materials, and the sinter production test was carried out. Based on the condition that the carbonaceous interior granulated particles are not mixed, the specific production rate was calculated. In addition, the segregation of the carbonaceous interior granulated particles in the layer height direction was adjusted to the segregation behavior of the actual machine investigated in advance. FIG. 2 shows the test results. As shown in FIG. 2, the specific production rate is a value obtained as 1.0 when the blending ratio of the carbonaceous interior granulated particles is 0.

When the specific surface area is 500 cm ² / g, the carbonaceous material decorated granulated particles having an outer layer of iron ore fines of 800 cm ² / g, also decreases the specific production rate than the base conditions due to the amount thereof, formulated to 30 mass%, 500cm about 10% ² / g, 800 cm to about 5% productivity ² / g was reduced. On the other hand, in the example of 1000 cm ² / g ^{of the present invention, 1500 cm 2} / g, 2200 cm ² / g, almost no decrease in the production rate was observed ^{, and in Example 3 of 2200 cm 2} / g, the carbonaceous material interior granulation was performed. Despite blending 30 mass% of particles, the production rate increased by about 5%.

<Example 2: Relationship between the specific surface area of iron ore powder constituting the outer layer of the carbonaceous interior granulated particles and the drop strength and crush strength>
In this test, carbonaceous interior granulated particles were prepared using concentrate fine particles having different specific surface areas, and the strength of the granulated particles was measured. Table 2 shows the values of the specific surface area and the strength test results of the concentrate fine powder used. The specific surface area was measured according to the brain air permeation method specified in JIS R 5201.

A dish-type granulator (also referred to as a pan pelletizer) having a diameter of 600 mm was used to prepare the carbonaceous interior granulation particles to be used for the strength test. A raw material powder obtained by mixing coke having a diameter of 3 to 5 mm, concentrate fine powder having a different specific surface area, and quicklime (5 mass%) as a CaO source is put into the granulator, and granulated while sprinkling water to achieve a diameter. Wet pellets made of carbonaceous material having a water content of 12 to 14 mm and a water content of 8 to 10 mass% were prepared.

The carbonaceous material interior granulated particles were subjected to a drop strength test and a crush strength test in a wet state. The drop strength test is a test of resistance to drop impact such as transfer of a belt conveyor during transportation, and is widely used as a method for measuring the strength of carbonaceous interior granulated particles mainly composed of iron ore powder. It is a thing. The test method is to freely drop the target carbonic material interior granulated particles from a height of 45 cm onto an iron plate, and visually confirm the cracks on the surface of the carbonaceous material interior granulated particles by the impact of the drop, or the said. The number of drops required for the granulated particles inside the carbonaceous material to be destroyed is counted, and the number of drops is taken as the drop strength. In this test, the drop strength test of 10 carbonaceous interior granulated particles was carried out, and the average number of drops was taken as the drop strength.

In the crushing strength test, a load is gradually applied from above the carbonaceous interior granulated particles using an autograph tester, and the load (kgf) at the time when the carbonaceous interior granulated particles are destroyed is the crushing strength. This is for testing the resistance to the load applied to the carbon material interior granulation particles when the packed layer is formed by laying the carbon material interior granulation particles.

The strength standard that the carbonaceous interior granulated particles should have in order to withstand the load when forming the packed bed in the transport and firing process after granulation is based on the many years of operation experience of the iron ore pellet plant. Generally, the strength is 5 times or more, and the crushing strength is 1 kgf or more. As a result of this test, when the specific surface area of the concentrate fine powder was 54 cm ² / g, all the carbonaceous material interior granulated particles collapsed in one drop, and the crushing strength could not be measured. When the specific surface area is ^{391 cm 2} / g and 518 cm ² / g, both the drop strength and the crush strength are less than the above standard values, but when the ^{specific surface area is 1009 cm 2} / g, the drop strength is 5.5 times and the crush strength is 1.04 kgf. Strength above the standard value was obtained. Further, when the specific surface areas were 1527 cm ² / g and 2127 cm ² / g, both the drop strength and the crush strength were improved.

From the results of Examples 1 and 2 described above, by setting the specific surface area of the iron ore powder constituting the outer layer of the carbonaceous interior granulated particles to 1000 cm ² / g or more, the specific productivity, drop strength and crush strength can be determined. It can be seen that both are good.

According to the sinter interior granulated particles for producing the sinter of the present invention, high productivity is achieved by producing the sinter using the sinter raw material containing the sinter interior granulated particles according to the present invention. High-grade sinter can be obtained. Therefore, by using the sinter obtained as a raw material for the blast furnace, it is possible to operate the blast furnace with high productivity.

Claims (3)

It is a carbonaceous material interior granulated particle for sinter production, which has a carbonaceous material core and an outer layer in which the periphery of the coal material core is coated with a mixed powder composed of iron ore powder and CaO source powder, and is the iron ore powder. , The carbonaceous interior granulated particles for sinter production, characterized in that the specific surface area measured by the brain air permeation method specified in JIS R 5201 ^{is 1000 cm 2 / g or more.} The charcoal for producing sinter according to claim 1, wherein the CaO source powder is a CaO-containing raw material such as quicklime, limestone, or dolomite, and the CaO content in the mixed powder is 10 mass% or less. Material Interior granulated particles. The carbonaceous interior granulated particles for producing sinter according to claim 1 or 2 are merged with other granulated particles for sintering to mix both granulated particles, and then the mixed granulated particles. A method for producing sinter, which is characterized in that sinter is obtained by charging the particles into a sinter and sintering the particles.

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