JP7073959B2 - Sintered ore manufacturing method - Google Patents

Description

The present invention relates to a method for producing a sinter.

In a blast furnace, sinter containing an iron source and coke as a reducing agent are laminated in the furnace, and hot air is blown from the tuyere to reduce the sinter to obtain pig iron.

Sintered ore is obtained by mixing iron ore as an iron source with limestone, which is a slag-forming material, granulating and sintering, and the required strength is secured by sintering. ..

Since the resources of high-grade iron ore have been depleted in recent years, low-grade, inferior iron ore is increasingly used for sinter production. Due to such deterioration of iron ore, the gangue component in the sinter is increasing.
As the gangue component in the sinter increases, the slag ratio in the blast furnace increases. As the slag ratio in the blast furnace increases, the energy required to dissolve the increased slag increases.
As the required energy increases, it is necessary to increase the reducing agent ratio. In addition, an increase in the slag ratio causes an increase in the amount of melt in the fusion zone, resulting in deterioration of air permeability in the blast furnace. If the air permeability of the blast furnace deteriorates, the amount of air blown must be reduced, so that the amount of tapping in the blast furnace cannot be maintained.

As a method of suppressing the increase in gangue components due to the deterioration of iron ore, pellets (cement bond pellets, sometimes referred to as calcined pellets to distinguish them from raw pellets before calcination) are mixed with the sinter. The method is being considered. This is because most of the pellets on the market have a lower content of gangue components than iron ore.
Here, the pellets on the market include acidic pellets and basic pellets. Since acidic pellets soften at a lower temperature than sinter when heated, there is a problem that when sinter containing acidic pellets is charged into a blast furnace, the thickness of the cohesive zone increases and the pressure loss of the blast furnace increases. there were.
However, since pellets are made by granulating powdered iron ore into a spherical shape and then firing it to perform solid-phase sintering, the amount of gangue is small, and the amount of basic pellets produced by adding CaO components to adjust the components and sintering them. Is less than acidic pellets. Therefore, if only basic pellets are used as pellets, there is also a problem that most of the calcined pellets that can be procured on the market cannot be used.

Therefore, conventionally, techniques have been studied in which powdered iron ore used for pellet production is used as a raw material for sinter, and calcined pellets themselves are used as a raw material for sinter. For example, Patent Document 1 describes that a semi-pellet outer shell, which is a non-baked pellet, coated with CaO is used as a raw material for sinter (Patent Document 1).
Non-Patent Documents 1 and 2 describe that the air permeability is improved by arranging the coarse particles containing the calcined pellets in the sintered raw material layer.
Patent Document 2 describes that coarse-grained iron ore having a particle size of 8 to 30 mm is added to a sinter raw material having a weight ratio of 2 to 10%. It is also stated that the coarse-grained iron ore may be pellets.
Patent Document 3 describes that the calcined pellet is contained in the compounding raw material in an amount of less than 6%.
Patent Document 4 describes that one or more kinds of small lump ore, small lump slag, small lump medium solvent and small lump pellets having a particle size of 8 to 15 mm are blended in the sinter raw material.

Japanese Unexamined Patent Publication No. 59-31834 Japanese Unexamined Patent Publication No. 62-248888 Japanese Unexamined Patent Publication No. 2016-74497 Japanese Patent No. 1956822

ISIJ Int., 45 (2005), 538-543 Iron and Steel, 92 (2006), 779-787

However, the techniques described in Patent Documents 1 to 4 and Non-Patent Documents 1 and 2 have the following problems.
Since the pellet used in Patent Document 1 is a non-calcined pellet, it cannot be applied when a calcined pellet is used.
Non-Patent Documents 1 and 2 and Patent Documents 2 to 4 describe the use of calcined pellets, but describe changes in pressure loss when the sinter and / or pellets after calcining are used in a blast furnace. It is unclear whether the increase in pressure loss of the blast furnace due to acidic pellets can be suppressed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a sinter in which pressure loss is unlikely to increase when used in a blast furnace operation even if acidic pellets are contained as a raw material.

The method for producing a sinter of the present invention includes a mixed granulation step of mixing and granulating a sinter raw material containing an acidic pellet with a return ore and a coagulant to produce a granulated product, and baking the granulated product. The sintering step of binding is carried out, and the mixed granulation step is characterized by including a step of coating the surface of the acidic pellet with a raw material containing 30% by mass or more of the CaO component.
In the present invention, since the surface of the acidic pellet, which is one of the raw materials for sintering, is coated with CaO, the acidic pellet becomes basic by melting and assimilating with CaO at the time of sintering. Therefore, when the blast furnace is charged, the softening and melting temperature is close to that of the basic pellets, and the pressure loss is unlikely to increase when used for blast furnace operation.

In the present invention, the ratio of the mass of the acidic pellets to the total mass (referred to as pure raw material) of the sinter raw material and the returned ore is preferably more than 0% and less than 30% by mass.
According to the present invention, since the mass ratio of the acidic pellets to the pure raw material is less than 30% by mass, the acidic pellets can be used without lowering the production rate of the sinter.

In the present invention, the mixed granulation step includes a coating step of coating the surface of the acidic pellet with a raw material containing 30% by mass or more of CaO component, and a granulator for other sintering raw materials, the return ore and the coagulant. By mounting the acidic pellets coated in the other raw material granulation step, the acidic pellets coated in the coating step, and the other raw materials granulated in the other raw material granulation step on the conveyor so as to overlap each other on the conveyor. It is preferable that the step of mixing and granulating the raw materials for sintering by carrying out the mixing step of mixing and mixing.
In the present invention, the coated acidic pellets and other raw materials are mixed by transferring a plurality of conveyors during transportation. Therefore, during the mixed granulation of the sintered raw material, the sintered raw material can be mixed without peeling the CaO coated from the surface of the acidic pellet.

The schematic diagram of the manufacturing apparatus used in the manufacturing method of the sinter according to this embodiment. The flow chart which shows the procedure of the manufacturing method of the sinter which concerns on this embodiment. The detailed view of S1 of FIG. Conceptual diagram of load softening test equipment. The figure which shows the relationship between temperature, gas, load and time of the load softening test of an Example. The figure for demonstrating how to obtain a KS value.

Hereinafter, embodiments suitable for the present invention will be described in detail with reference to the drawings.

(material)
First, the raw materials used in the method for producing sinter according to the present embodiment will be described.
The raw material used in the method for producing a sinter according to the present embodiment is any other as long as it contains an acidic pellet and a coating material (a raw material containing 30% by mass or more of CaO component) that covers the surface of the acidic pellet. The raw material is not particularly limited. Known raw materials can be used.
The acidic pellet means a pellet having a basicity of less than 0.9. The basicity means the mass ratio CaO / SiO ₂ of CaO and SiO ₂ in the substance.

In this embodiment, the raw materials are classified as follows.
Auxiliary raw materials: Limestone, fresh lime, sardine, etc. Miscellaneous raw materials: Dust scale New raw materials (raw materials for sintering): Iron ore, pellets, coke, auxiliary raw materials, total return of miscellaneous raw materials: After manufacturing sintered ore Pure raw material under the sieve classified with a 5 mm sieve: Total of new raw material and return ore Coagulant: Charcoal material such as coke breeze and smokeless coal that is a heat source in the sintering process All raw materials: Pure raw material Total blended raw material with coking material: Raw material blended in the desired ratio. Alternatively, the description of the raw material is as described above in the state immediately before the granulation is completed by adding water to the mixture of the raw materials in a desired ratio and the raw materials are charged into the pallet of the sintering machine.

(manufacturing device)
Next, with reference to FIG. 1, the outline of the manufacturing apparatus used in the method for manufacturing the sinter according to the present embodiment will be described.

As shown in FIG. 1, the manufacturing apparatus 100 includes a main line 10, a pellet granulation line 20, and a sintering machine 6.

The main line 10 is a line for granulating raw materials other than acidic pellets and a coating material, and includes a first raw material tank group 1, a first granulator 3, a first collecting conveyor 22, and a second collecting conveyor 24.
The first raw material tank group 1 is a storage layer for storing raw materials and cutting them out to a first collecting conveyor 22 as needed. The raw materials stored in the first raw material tank group 1 include iron ore, auxiliary raw materials, miscellaneous raw materials, return ores, and coagulants.

The first collecting conveyor 22 is a conveyor that conveys the raw materials cut out from the first raw material tank group 1 to the first granulator 3, and is provided below the first raw material tank group 1. As the first collecting conveyor 22, for example, a belt conveyor is used.

The first granulator 3 is a device for adding water to the raw materials transported from the first collecting conveyor to mix and granulate, and is provided at the end of the first collecting conveyor 22 in the transport direction. As the first granulator 3, for example, a drum mixer is used.

The second collecting conveyor 24 is a conveyor that conveys the raw materials granulated by the first granulator 3 and the raw materials granulated by the pellet granulation line 20 to the sintering machine 6, and is the first granulator 3. A start end in the transport direction is provided at the discharge port of. As the second collecting conveyor 24, for example, a belt conveyor is used.

The pellet granulation line 20 is a line for granulating acidic pellets, and includes a second raw material tank group 2, a third collecting conveyor 26, a second granulating machine 4, and a fourth collecting conveyor 28.

The second raw material tank group 2 is a storage layer for storing raw materials and cutting them out to the first collecting conveyor 22 as needed. The raw materials stored in the first raw material tank group 1 include acidic pellets, a coating material, and a binder added as needed.

The third collecting conveyor 26 is a conveyor that conveys the raw materials cut out from the second raw material tank group 2 to the second granulator 4, and is provided below the second raw material tank group 2. As the third collective conveyor 26, for example, a belt conveyor is used.

The second granulator 4 is an apparatus for mixing and granulating the raw materials conveyed from the third collecting conveyor 26. Here, it is a device that coats the surface of the acidic pellet with a coating material. The second granulator 4 is provided at the end of the third collecting conveyor 26 in the transport direction. As the second granulator 4, for example, a drum mixer is used.

The fourth collecting conveyor 28 is a conveyor that conveys the raw materials granulated by the second granulating machine 4 to the second collecting conveyor 24, and the starting end in the transport direction is provided at the discharge port of the second granulating machine 4. The end is provided above the second collecting conveyor 24 and between the start and end points in the transport direction. As the fourth collective conveyor 28, for example, a belt conveyor is used.

The sintering machine 6 is an apparatus for producing sinter by sintering raw materials, and a hopper (not shown) is connected to the end of the second collecting conveyor 24. The structure is not particularly limited as long as it can produce sinter, but a DL (dwightroid) sinter machine can be exemplified.
The above is the outline of the manufacturing apparatus 100.

(Outline of manufacturing method)
Next, an outline of the method for producing a sinter according to the present embodiment will be described with reference to FIG.
First, a sintering raw material containing acidic pellets is mixed with a return ore and a coagulant and granulated to produce a granulated product (S1 in FIG. 2, mixed granulation step).
Next, the granulated product is sintered (S2 in FIG. 2, sintering step).
The above is the outline of the method for producing sinter according to the present embodiment.

(Details of manufacturing method)
Next, the details of the method for producing the sinter according to the present embodiment will be described with reference to FIG.
<S1: Mixed granulation process>
In S1, a sintering raw material containing acidic pellets is mixed with a return ore and a coagulant and granulated to produce a granulated product.
Specifically, first, the raw material is granulated by the pellet granulation line 20 and the main line 10.

First, the granulated product to be granulated by the pellet granulation line 20 will be described.
In the pellet granulation line 20, the surface of the acidic pellet is covered with a coating material.

The reason for coating the acidic pellets is to raise the softening temperature. The cause of softening and melting of acidic pellets from low temperatures is the presence of low melting point minerals containing SiO ₂ , as mentioned in Kemppainen et al .: Iron and Steel, 103 (2017), 175, etc. By coating the acidic pellets with a material containing CaO, the acidic pellets react with CaO during the sintering reaction to become a mineral having a high melting point, and the softening temperature can be raised.

The basicity is preferably 0.9 or more for the pellets after coating. This is because the softening and melting temperature can be raised to the same temperature as the basic pellets.
The blending amount of the acidic pellets is preferably such that the ratio to the total mass of the pure raw material is more than 0% and less than 30% by mass. This is because if it is 30% by mass or more, the productivity may decrease.

The type of the covering material is not particularly limited as long as it contains 30% by mass of the CaO component. When the content is 30% by mass or more, the coating layer can be made thin, the adhesion to the acidic pellets is increased, and the reaction is easy. Further, when the adhesive layer becomes thin, the granulation time required to reach the target basicity can be shortened. Further, the content of a substance that lowers the basicity such as SiO ₂ as a component of the coating layer is reduced.
Specific coating materials include quicklime (CaO), limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), dolomite (CaMg (CO ₃ ) ₂ ), and mixtures thereof.
From the viewpoint of ease of coating and ease of increasing basicity, a high CaO component is preferable, and quicklime (CaO) is most preferable. However, quicklime is more expensive than other dressings, so other materials may be selected in consideration of cost.

The particle size of the covering material is not particularly limited, but it is preferably less than 1 mm (under a sieve classified by a sieve having a mesh size of 1 mm). This is because the coating becomes easy.

When a material other than CaO is used as the covering material, CaO may be used as a binder in an amount of about 2% by mass with respect to the mass of the pellets after coating. This facilitates coating.

The specific granulation procedure is as follows.
First, acidic pellets, a covering material, and a binder, if necessary, are cut out from the second raw material tank group 2 and conveyed to the second granulator 4 by the third collecting conveyor 26 (S21 in FIG. 3).
Next, the cut raw material is granulated by the second granulator 4, and the surface of the acidic pellet is coated with a coating material (S22 in FIG. 3, coating step).
The coated pellets are discharged from the second granulator 4 and conveyed by the fourth collecting conveyor 28 toward the second collecting conveyor 24.
The above is the details of the granulated product to be granulated by the pellet granulation line 20.

Next, the granulated product granulated on the main line 10 will be described.
In the main line 10, raw materials other than the acidic pellets and the dressing are granulated.
Raw materials other than acidic pellets and coating materials are iron ore, auxiliary raw materials, miscellaneous raw materials, coagulants, and binders.

The specific granulation procedure is as follows.
First, raw materials are cut out from the first raw material tank group 1 and conveyed to the first granulator 3 by the first collecting conveyor 22 (S23 in FIG. 3).
Next, the cut raw material is granulated by the first granulator 3 (S24 in FIG. 3, other raw material granulation step).
The granulated product is discharged from the first granulator 3 and conveyed to the sintering machine 6 on the second collecting conveyor 24.
The above is the description of the granulated product to be granulated on the main line 10.

Next, the raw material granulated on the pellet granulation line 20 and the raw material granulated on the main line 10 are mixed (S25 in FIG. 3, mixing step).
Specifically, the raw material granulated by the pellet granulation line 20 conveyed by the fourth collecting conveyor 28 is overlapped on the raw material granulated by the main line 10 being conveyed by the second collecting conveyor 24. It is mounted on the second collecting conveyor 24 and mixed.
In a collective conveyor, a plurality of belt conveyors are generally connected in a stepwise manner so as to gradually decrease in height. Therefore, the raw material granulated on the main line 10 and the raw material granulated on the pellet granulation line 20 can be mixed by the impact when the raw material falls from the end of the conveyor on the upstream side to the start end of the conveyor on the downstream side. .. A separate granulator or the like is not always necessary. This is because if too much external force is applied during granulation, the coating material may peel off from the surface of the acidic pellets.
The mixed raw materials are finally transferred from the collecting conveyor to a hopper (not shown) of the sintering machine 6.
The above is the details of S1.

<S2: Sintering process>
In S2, the raw material granulated in S1 is sintered to produce a sinter.
The production method is not particularly limited as long as sinter can be obtained.

In the acidic pellets coated with the coating material, the pellets may solidify into coarse particles at the time of sintering. Even in this case, the sinter after sintering is crushed by the crusher, so that the coarse particles are crushed. Therefore, there is little risk that the coarse particles will be put into the blast furnace as they are.

Further, even when the pellets are solidified during sintering, as described in Non-Patent Documents 1 and 2, by arranging the coarse particles in the sintering raw material layer, the air permeability is improved, which adversely affects the sintering. The risk of exerting is small.
The above is the details of S2.

As described above, according to the present embodiment, since the acidic pellets are coated with CaO and used as a raw material for sintering, the acidic pellets are melt-assimilated with CaO at the time of sintering and become basic. Therefore, when the blast furnace is charged, the softening and melting temperature is close to that of the basic pellets, and the pressure loss is unlikely to increase when used for blast furnace operation.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to Examples.
Sintered ore was produced using CaO-coated acidic pellets as a raw material, and its softening characteristics and productivity were evaluated. The specific procedure is as follows.
First, acidic pellets were prepared as raw materials. The particle size of the acidic pellets was 8 to 13 mm, and the arithmetic mean diameter was 10 mm. The composition is as shown in Table 1.

Next, as the raw materials other than the acidic pellets, the raw materials shown in Table 2 were blended in the blending ratio shown in the “test conditions” of Table 2. The blending amounts of other powder ores and limestone were adjusted along with the increase in the blending amount of acidic pellets so that the basicity, SiO ₂ content, and Al ₂ O ₃ content of the product sinter were substantially constant.

In Examples 1 to 3, the acidic pellets were coated with limestone (CaO 56% by mass) as a CaO source and then mixed with other raw materials, and the blending amount of the acidic pellets was changed in the range of 10 to 30% by mass. Is. Comparative Example 1 does not contain acidic pellets. In Comparative Example 2, 10% by mass of acidic pellets were blended, but they were mixed at the same time as other raw materials without being covered with limestone.

The compounding was carried out according to the following procedure.
(Acid pellet coating)
A part of the limestone to be blended was weighed and mixed with the acidic pellet for 180 seconds with a drum mixer while adding water in another step, and the surface of the acidic pellet was coated with limestone. The amount of the coating layer was determined so that the basicity of the coating pellet was 1.0. However, in Comparative Examples 1 and 2, this step was not carried out.

(Granulation of the remaining raw material)
The raw materials other than the acidic pellets and the limestone constituting the coating layer were granulated by kneading with water for 180 seconds with a drum mixer.

(Mixing of compounding ingredients)
Finally, the coated pellets and the raw materials forming the powder layer were combined and mixed with a drum mixer for 15 seconds to prepare a compounding raw material. However, in Comparative Example 1, this step was not carried out.
In Comparative Example 2, uncoated acidic pellets were mixed in this step.

(Sintering test)
The sintering test was a pot sintering using a pot having a diameter of 300 mm and a depth of 500 mm.
First, a great was placed on the bottom of the pot, and 2 kg of sinter with a particle size of 10 to 15 mm was laid on it as a floor.
Next, the compounded raw material was put into a hopper, dropped from a position of 30 cm in height from the mouth of the pot, and charged into the pot to form a packed raw material having a charging density comparable to that of the actual machine.
After charging the packed raw material, the pot was placed on the windbox, and the surface of the packed bed of the raw material was heated for 1 minute with an LPG burner and ignited while sucking at a pressure under the pot of 9.8 kPa.
After ignition, firing was continued while sucking at 9.8 kPa, and firing was continued until 3 minutes after the exhaust gas temperature reached the maximum temperature. After 3 minutes, the suction was immediately stopped to stop the baking, and the sintered cake was cooled to room temperature in the air atmosphere as it was. After cooling is completed, the sintered cake is taken out and dropped from a height of 2 m four times, and then the crushed sintered cake is classified by a sieve having a sieve mesh of 5 mm, and the production rate is increased by using the sieve as an adult sintered ore. It was measured.

(Derivation of production rate)
The production rate was derived by the following formula, defining the firing time as the time from the start of ignition to the maximum temperature of the exhaust gas.
Production rate = (weight of sintered ore of 5 mm or more-weight of bedding) (t) / (cross-sectional area of pot (m ³ )) / firing time (h)
Further, the obtained production rate was standardized to a relative value when Comparative Example 1 in which no acidic pellet was blended was set to 100. The results are shown in the "Sintering production rate (relative value)" section of "Sinterability" in Table 3.

(Composition analysis)
The chemical composition of the sinter obtained as a result of the pot test was analyzed by a known composition analysis method. The results are shown in the section "Sintered ore chemical composition" in Table 3.

(Sintered ore softening property test)
Next, the obtained sinter was subjected to a load softening test, and the softening and melting behavior in the atmosphere near the cohesive zone was investigated. The test method was based on the paper by Mochizuki et al. (Iron and Steel, 72 (1986), 1855.).
First, as an apparatus, the load softening test apparatus 300 shown in FIG. 4 was prepared.
As shown in FIG. 4, the load softening test device 300 includes a vertical electric furnace 301, a graphite pit 302, a graphite heating element 305, a load control device 306, a temperature measuring device 307, a gas pressure measuring device 308, and a dropping sample saucer 309. A gas flow rate control device 310 and an exhaust gas analyzer 312 are provided.

The vertical electric furnace 301 is a cylindrical electric furnace. The graphite crucible 302 is a cylindrical crucible into which the charge sample 303 is charged, and is housed in the vertical electric furnace 301. The graphite crucible 302 has an inner diameter of 70 mm and is provided with a rostrum 303A (grate) for introducing gas at the bottom.

The graphite heating element 305 is a heater for heating the charge sample 303, and is provided so as to surround the outer periphery of the graphite crucible 302.
The load control device 306 is a member that applies a load to the charge sample 303, and is provided here at the open end of the graphite crucible 302 and includes a load applying means called a punch rod that applies a load in the axial direction of the graphite crucible 302. .. The load control device 306 also includes a discharge port 303B for discharging gas.

The temperature measuring device 307 is a thermocouple for measuring the temperature of the charged sample 303, and is provided on the lower surface of the load control device 306 (upper surface of the charged sample 303).
The gas pressure measuring device 308 is a device that measures the gas pressure of the reducing gas 304 introduced into the graphite crucible 302 and the exhaust gas 311 after the reduction reaction exhausted from the graphite crucible 302.

The dripping sample saucer 309 is a saucer when the ore layer melted during the test is dropped, and is provided below the rostrum 303A.
The gas flow rate control device 310 is a device that controls the gas flow rate of the reducing gas 304.
The exhaust gas analyzer 312 is an apparatus for analyzing the composition of the exhaust gas 311 and uses an infrared spectroscope.
500 g of sinter was charged into the load softening test apparatus 300, and the temperature, gas, and load were applied under the conditions shown in FIG. At this time, from the relationship between the time shown in FIG. 6 and the ventilation resistance index, the portion corresponding to the area of the shaded area in FIG. 6 was defined as the ventilation resistance coefficient KS value and obtained from the following equations (1) and (2). ..

here,
KS: High temperature part ventilation resistance index (SI unit, ℃)
t: temperature (° C)
K (t): Ventilation resistance index (SI unit) at temperature t
t _mf : Dropping end temperature (° C), here 1600 ° C
ΔP: Pressure drop (Pa)
h: Layer height (m)
ρ _g : Gas density (kg / m ³ ) * Temperature function μ _g : Gas viscosity (kg / m ・ s) * Temperature function
u _g : Gas superficial velocity (m / s) * Temperature function β: Coefficient determined by gas flow, 0.2 here

The KS value is a ventilation resistance index calculated from the pressure loss curve of the load softening test, and the larger the KS value, the lower the air permeability. It has been reported that when an iron source raw material showing a large KS value in a load softening test is used in a blast furnace, the pressure loss of the blast furnace increases, and a charge having a low KS value is desired in blast furnace operation. Therefore, the aeration resistance coefficient was evaluated by a relative value when the KS value of the acidic pellet alone was set to 100. The results are shown in the "KS value" section of the "Load softening test" in Table 3.

(Test results)
The KS value showed the same result as in Comparative Example 1 in which the acidic pellet was not blended in Examples 1 to 3. It is considered that this is because when the acidic pellets were coated with limestone and sintered in a pan, they were modified to increase the softening temperature and the decrease in air permeability was suppressed.

In Comparative Example 2, the KS value was larger than that of the other examples. It is probable that this was because the acid pellets were not coated, so that the basicity did not increase and the softening start temperature did not increase.

As is clear from Comparative Example 1, Example 1, and Example 2, the production rate of the sinter increased with the increase of the acidic pellet compounding amount up to 20% by mass of the acidic pellet compounding amount. It is considered that this is because the air permeability of the sintered bed improved with the increase of acidic pellets.

In Example 3, 30% by mass of acidic pellets were blended, and the KS value was about the same as in Examples 1 and 2, but the production rate was lower than in Examples 1 and 2. It is considered that this is because the sinter was discharged without being sufficiently sintered as a result of the excessive increase in air permeability and the shortening of the firing time due to the compounding of the acidic pellets.

From the above results, it was found that the acidic pellets can be modified so that the softening and melting temperature becomes high by coating the acidic pellets with a coating material containing CaO.
Furthermore, it was found that the productivity of the sinter can be improved by firing in a sinter with the amount of coated pellets in the sinter compounding raw material set to less than 30% by mass.

1 ... 1st raw material tank group, 2 ... 2nd raw material tank group, 3 ... 1st granulation machine, 4 ... 2nd granulation machine, 6 ... Sintering machine, 10 ... Main line, 20 ... Pellet granulation line, 22 ... 1st collective conveyor, 24 ... 2nd collective conveyor, 26 ... 3rd collective conveyor, 28 ... 4th collective conveyor, 100 ... Manufacturing equipment.

Claims (2)

A mixed granulation process in which a raw material for sintering including acidic pellets , which are calcined pellets, is mixed with a return ore and a coagulant and granulated to produce a granulated product.
The sintering process of sintering the granulated product and
And carry out
The mixed granulation step includes a step of coating the surface of the acidic pellet with a raw material containing 30% by mass or more of CaO component.
A method for producing a sinter, wherein the ratio of the mass of the acidic pellets to the total mass of the raw material for sinter and the returned ore is more than 0% and less than 30% by mass . The mixed granulation step is
A coating step of coating the surface of the acidic pellet with a raw material containing 30% by mass or more of CaO component, and
Other raw material granulation processes for granulating other raw materials for sintering, the returned ore and the coagulant with a granulator, and
A mixing step of mixing the acidic pellets coated in the coating step and the other raw materials granulated in the other raw material granulation step on the conveyor by mounting them on the conveyor so as to overlap each other.
The method for producing a sinter according to claim 1, wherein the step is a step of mixing and granulating the raw materials for sinter.

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