CN108350513B

CN108350513B - Method for charging raw material into blast furnace

Info

Publication number: CN108350513B
Application number: CN201680062479.9A
Authority: CN
Inventors: 市川和平; 柏原佑介; 大山伸幸; 石井邦彦
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2015-10-28
Filing date: 2016-10-25
Publication date: 2020-05-22
Anticipated expiration: 2036-10-25
Also published as: TR201805266T1; JP6260751B2; JPWO2017073053A1; KR102090886B1; WO2017073053A1; KR20180058813A; BR112018008267B1; BR112018008267A2; CN108350513A

Abstract

The invention provides a method for charging raw materials, which can improve the reactivity in a blast furnace and can further reduce the reducing agent ratio. When a coke layer is formed by charging coke in an amount of 25 to 80 mass% of the total coke amount in a primary charge into a blast furnace, and then a mixed raw material obtained by mixing the remaining coke in the primary charge with an ore material containing acid pellets in an amount of 10 mass% or more of the ore material in the primary charge is charged onto the coke layer in 2 batches, the particle size of the coke mixed in the 1 st batch is in the range of 15 to 40mm, the 1 st batch is charged in the range of a non-dimensional radius of a furnace mouth of 0 to 0.8, and the remaining mixed raw material is charged as the 2 nd batch in the range of a non-dimensional radius of a furnace mouth of 0.6 to 1.0.

Description

Method for charging raw material into blast furnace

Technical Field

The present invention relates to a method for charging a blast furnace with a raw material by using a rotary chute.

Background

In recent years, reduction of CO is required from the viewpoint of prevention of global warming₂And (4) discharging the amount. In the iron and steel industry, CO₂About 70% of the emissions are generated by the blast furnace, requiring a reduction in the blast furnace CO₂And (4) discharging the amount.

In general, a blast furnace is charged with an ore material such as sintered ore, pellet ore or lump ore and coke alternately in layers from a furnace top, and a combustion gas is flowed through a tuyere to obtain pig iron. The charged blast furnace charging materials, i.e., coke and ore-like materials, descend from the furnace top to the belly of the blast furnace, causing reduction of the ore and temperature rise of the materials. The ore material layer (hereinafter, also simply referred to as a "ore layer") is gradually deformed while filling the gaps between the ore materials due to the temperature rise and the load from above, and forms a so-called weld layer having a very large air flow resistance and hardly flowing gas in the belly of the blast furnace.

Generally speaking, CO in blast furnaces₂The reduction in the amount of emissions can be achieved by a reduction in the reducing agents (coke, pulverized coal, natural gas, etc.) used in the blast furnace.

However, when the reducing agent, particularly coke, is reduced, the layer thickness of the coke layer is reduced, and the gas flow resistance is increased in the reflow zone where the ore is softened and melted. The ventilation resistance of the reflow zone, which greatly affects the ventilation performance of the entire blast furnace, is known empirically to prevent stable operation of the blast furnace when the ventilation resistance of the reflow zone increases.

Therefore, various measures for improving the air flow resistance of the reflow tape have been studied. Further, in order to improve the aeration resistance of the reflow zone, it is known that it is effective to mix coke in the ore layer, and many inventions for mixing coke in the ore layer have been reported.

For example, patent document 1 discloses the following technique: in a bell-less blast furnace, coke is charged into a hopper on the downstream side of an ore hopper, the coke is deposited on ore on a conveyor belt, and then the ore and coke are charged into a top bunker, and the blast furnace is charged with the ore and coke through a rotary chute.

Patent document 2 discloses the following technique: the ore and the coke are separately stored in the silo of the furnace top and the coke and the ore are simultaneously charged in a mixed manner, whereby 3 kinds of batches, i.e., the charging batch for coke, the charging batch for center charging of coke, and the charging batch for mixed charging, are simultaneously performed.

Further, patent document 3 discloses, as a method for charging a raw material into a blast furnace, the following technique: in order to prevent the instability of the shape of the reflow zone and the decrease of the gas utilization rate near the center portion during the operation of the blast furnace and to achieve stable operation and improvement of the heat efficiency, all the ores and all the cokes are completely mixed and then charged into the blast furnace as a raw material.

Patent document 4 discloses the following technique as a means for enjoying the reactivity improvement effect by the coke blend: the reactivity of a blast furnace is improved by mixing highly reactive coke with an ore having low JIS reducibility to efficiently react the ore having low reactivity.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 3-211210

Patent document 2: japanese patent laid-open publication No. 2004-107794

Patent document 3: japanese laid-open patent publication No. 53-152800

Patent document 4: japanese laid-open patent publication No. 7-76366

Disclosure of Invention

Here, generally, in the interior of the blast furnace, gas flows easily in both the radially central portion and the peripheral portion of the furnace opening, and gas flows hardly in the furnace wall-side intermediate portion, so that there is a gas flow distribution in the radial direction of the blast furnace. Therefore, it is necessary to design the coke mixing ratio and the radial arrangement of the properties of the mixed coke based on the gas flow distribution.

However, patent documents 1 to 3 only describe means for mixing coke into the ore layer, and do not show a preferable coke mixing ratio distribution in the radial direction of the blast furnace.

Patent document 4 only describes reactivity of coke and ore and the maximum particle size thereof, but neither clearly shows a preferable mixing ratio of coke and ore nor a preferable distribution in the radial direction of the furnace mouth.

Further, recently, the use of acid pellets has increased because of the need for larger raw materials, but the use of acid pellets involves an increase in the reducing agent ratio and a decrease in the air permeability.

Therefore, in order to further improve the aeration resistance of the reflow zone when using the acid pellets, it is necessary to newly construct a preferable distribution of the mixed coke in the furnace.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a raw material charging method in which, in general, a large amount of gas flows in a central portion and a peripheral portion in a furnace mouth radial direction and a small amount of gas flows in an intermediate portion in the furnace mouth radial direction, and therefore, focusing on these gas flows, a large amount of coke having good reactivity and a small particle diameter is present in the intermediate portion in the furnace mouth radial direction where the gas flows are small, whereby the reactivity in the furnace can be improved and the reducing agent ratio can be further reduced.

That is, the gist of the present invention is configured as follows.

1. A method of charging a blast furnace with a raw material, comprising charging a blast furnace with an ore-based raw material and coke using a rotary chute at each charging,

and charging 25 to 80 mass% of coke in the total coke amount in the primary charge into a blast furnace to form a coke layer, and then charging a mixed raw material obtained by mixing the remaining coke in the primary charge and an ore-based raw material containing acid pellets, which is 10 mass% or more of the ore-based raw material in the primary charge, onto the coke layer in 2 batches, wherein the particle size of the coke mixed in the 1 st batch is in the range of 15 to 40mm, the 1 st batch is charged in the range of a non-dimensional radius of a furnace mouth of 0 to 0.8, and the remaining mixed raw material is charged in the range of a non-dimensional radius of a furnace mouth of 0.6 to 1.0 as the 2 nd batch.

2. The method for charging a raw material into a blast furnace according to the above 1, wherein a reactivity index CRI of the coke mixed in the 1 st batch is set to 35% or more.

3. The method of charging a blast furnace with a raw material according to 1 or 2, wherein an amount of the coke mixed in the 1 st batch is 70 mass% or more of an amount of the coke mixed with the ore-based raw material.

According to the present invention, since a large amount of coke having good reactivity and a small particle size is mixed at a position where the gas flow is small, the reactivity in the furnace can be improved and the reducing agent ratio can be further reduced.

Drawings

FIG. 1 is a diagram showing the gas flow velocity distribution in a blast furnace.

FIG. 2 is a view showing the state of the raw material deposition in the blast furnace.

Detailed Description

The present invention will be specifically described below.

In the present invention, charging of an ore-based raw material and coke, which are raw materials charged into a blast furnace, into the blast furnace using a rotary chute is performed every time charging is performed. As the ore-based raw material, in addition to sintered ore and/or lump ore, acid pellet ore is used.

Here, the one-time charging in the present invention means that the following process is performed 1 time: a series of processes in which coke is charged to form a coke layer, and then a mixed material obtained by mixing an ore-based material and coke is charged to form a mixed layer.

Here, a bell-less charging device having a known and common rotary chute may be used for charging the raw material into the blast furnace.

The ore raw materials and the coke are respectively stored in a furnace top bin. Further, the charging order of their raw materials from the top bin is as follows.

First, coke is charged.

That is, when the charging destination of the raw material in the rotary chute is moved from the center of the blast furnace toward the inner peripheral portion of the wall of the blast furnace, only coke is charged from the top bunker in which only coke is stored, thereby forming a coke layer.

In this case, the central coke layer may be formed in the central portion of the blast furnace, or the peripheral coke layer may be formed in the inner peripheral portion of the furnace wall with a furnace mouth dimensionless radius of 0.6 to 1.0 from the furnace wall portion (furnace mouth dimensionless radius: 1.0) toward the central shaft portion (furnace mouth dimensionless radius: 0).

The coke charge amount here is 25 to 80 mass% of the total coke amount in the above-mentioned primary charge. That is, in order to ensure the air permeability of the coke layer, it is necessary to use coke in an amount of at least 25 mass% of the total coke amount in the primary charge as the coke layer. On the other hand, in order to obtain the effect of improving the air permeability and the reducibility by the mixed coke by setting the coke amount in the primary charge charged by mixing with the ore-based raw material to 20 mass% or more, it is necessary to set the coke layer to 80 mass% or less.

Then, the coke and the ore-based raw material are discharged from the top bunker at the same time, and the blast furnace is charged with the mixed raw material of the coke and the ore-based raw material through the rotary chute. At this time, the mixed raw material was charged from the center axis of the blast furnace toward the inner peripheral portion of the furnace wall (the dimensionless radius of the furnace mouth: 1.0) by moving the rotary chute from a position close to the center axis of the blast furnace, that is, from a position at which the dimensionless radius of the furnace mouth is 0, to the outside in order from the center axis of the blast furnace.

The ore material charged into the blast furnace is acid pellets in which 10 mass% or more of the ore material charged in the first charge, that is, the total weight of the ore material charged in the first charge (hereinafter, referred to as total ore), is contained.

This is because if the ratio of the acid pellets used is 10 mass% or more of the total ore, the increase in the reducing agent ratio and the deterioration in the air permeability become remarkable, but by applying the raw material charging method of the present invention, the increase in the reducing agent ratio and the deterioration in the air permeability can be suppressed, and further improvement can be achieved. From the viewpoint of preventing the blast furnace operation from being significantly deteriorated, the upper limit of the usage ratio of the acid pellets is preferably about 50 mass% of the total ore. In the present invention, the term "acidic pellets" means those pellets containing CaO and SiO₂The basicity represented by the ratio of (a) to (b) is 0.5 or less.

In the present invention, the ore-based raw material may be charged so as to contain a predetermined amount of the acid pellets and at least one of the sintered ore and the lump ore.

It is important to mix and charge the ore-based raw material with the remaining coke of the coke charged alone, that is, 20 to 75 mass% of the total coke amount in the primary charge.

This is because the effect of improving the air permeability and the reducing property by the mixed coke can be obtained by setting the coke amount in the primary charge charged by mixing with the ore-based raw material to 20 mass% or more. On the other hand, in order to maintain the air permeability of the blast furnace, it is also important to form a coke (single) layer, and if the mixed coke is 75 mass% or more, that is, if the coke layer is less than 25 mass%, it is difficult to maintain the air permeability.

Here, fig. 1 shows the gas flow distribution in a general blast furnace. As shown in fig. 1, it is known that a region where the dimensionless radius of the furnace opening is less than 0.4 and a region where the dimensionless radius of the furnace opening is 0.8 or more are filled with a large amount of coke as a spacer, and therefore, gas flows easily, and a region where the dimensionless radius of the furnace opening is 0.4 or more and less than 0.8 has a small amount of coke and is charged in a large amount in the ore layer, and therefore, gas does not flow easily, and therefore, there is a concern that the reduction reaction is delayed compared with other regions.

Therefore, in the present invention, in order to eliminate the delay of the reduction reaction in the region where the dimensionless radius of the throat is 0.4 or more and less than 0.8, the mixed raw material in which the coke and the ore-based raw material are mixed is charged into the blast furnace in 2 batches for each charge. Hereinafter, the charging step of the mixed raw materials into the blast furnace will be described in detail.

FIG. 2 shows the state of the raw material accumulation in the blast furnace according to the present invention.

In the present invention, when a mixed raw material of an ore-based raw material and coke is charged in 2 batches per charge, the 1 st batch is charged in the range of 0.0 to 0.8 of the dimensionless radius of the furnace opening, and the 2 nd batch is further charged in the range of 0.6 to 1.0 of the dimensionless radius of the furnace opening.

Further, it is the most important control factor in the present invention to set the particle size of the coke mixed in the 1 st batch to be in the range of 15 to 40 mm. This is because the reactivity in the reaction delay region can be improved if the coke having a particle diameter in the range of 15 to 40mm is segregated in the 1 st batch. That is, when the particle diameter of the coke mixed in the 1 st batch is less than 15mm, the particle diameter becomes too small and the ventilation of the blast furnace becomes poor. On the other hand, if the particle diameter of the coke exceeds 40mm, the particle diameter becomes too large and the reactivity is lowered, so that it is difficult to enjoy the improvement of the reducibility.

It should be noted that the coke of the 1 st batch does not need to have a particle size of 15 to 40mm in total, and even if a coke having a particle size of 15 to 40mm is mixed, the present invention is not affected if the mixing amount is about 5 mass% or less of the total amount of the coke of the 1 st batch.

On the other hand, the particle size of the coke of the 2 nd batch is not particularly limited, and a particle size of approximately the same size as that of the coke of the 1 st batch, for example, a particle size in the range of 15 to 50mm may be used.

In addition, as shown in FIG. 2, by carrying out the charging of the mixed raw materials according to the present invention, a position where 2 layers of the mixed layer formed of the mixed raw materials exist is formed on the coke layer. Specifically, the first mixed layer is formed by charging the 1 st batch into a region of 0.0 to 0.8 in terms of a dimensionless radius of the furnace opening, and the second mixed layer is formed by charging the 2 nd batch into a region of 0.6 or more in terms of a dimensionless radius of the furnace opening. In this way, it is important that the batch 2 is loaded to the furnace wall periphery where the gas flows easily.

As shown in fig. 1, the blast furnace has a large amount of coke in the portion of the furnace mouth having a dimensionless radius of less than 0.4 and more than 0.8, and has good air permeability, and therefore, the gas flow increases. In this gas flow, the reason why the charging positions of the mixed raw materials of the 1 st batch and the 2 nd batch are overlapped as described above is that the thickness of the layer is easily reduced at the charging start end of the 2 nd batch due to the deposition angle of the mixed raw materials, and therefore, in order to form a thickened portion in a region near the dimensionless radius of 0.8 of the furnace mouth, it is necessary to repeat charging of the mixed raw materials at about 0.6 to 0.8.

Further, if the reactivity index CRI of the coke mixed in the 1 st batch is set to 35% or more, the reactivity in the furnace can be further improved, and the blast furnace operation can be further stabilized, which is preferable. The upper limit of the reactivity index CRI is not particularly limited, but is about 40% industrially.

Further, by setting the amount of coke mixed in the 1 st batch to 70 mass% or more of the amount of coke mixed with the ore-based raw material, the reducibility of the 1 st batch charged to a position where the ore-based raw material is large can be improved. In addition, the entire amount of coke mixed with the ore-based raw material may be mixed in the 1 st batch, and in this case, the entire amount in the 2 nd batch may be the ore-based raw material.

Examples

In the embodiment, the charging of the raw material is performed at each charging by using a rotary chute. The amount of coke mixed with the ore raw material in the coke charged at one time is 10-80 mass% of the total coke amount, and the remaining coke is supplied to the coke layer. The mixed raw materials were set to 2 batches for each charge, and the charging positions of the mixed raw materials of the 1 st batch and the 2 nd batch were variously changed. The particle size of the coke mixed in the 1 st batch was also variously changed. In addition, the coke has a reactivity index CRI of 30-35%. Specific test conditions are shown in table 1.

In the examples, the raw materials used in the present invention used a raw material (sintered ore and/or lump ore) containing 58 mass% of an iron component as an ore-based raw material and a raw material containing 65 mass% of an iron component and containing CaO and SiO₂Has a CaO/SiO ratio of₂As the raw material, 0.05 wt% was used as the acid pellets, and as the coke, a coke containing 88 wt% of carbon was used.

The tapping ratio is the amount of tapping per day (t/d) of the blast furnace divided by the furnace volume (m)³) And the resulting value. The reducing agent ratio, coke ratio and pulverized coal ratio were the reducing agent amount, coke amount and pulverized coal amount (kg/t) used in the production of 1t of molten iron.

The average particle diameter (mm) of the mixed coke mixed with the ore-based raw material was an arithmetic average diameter, and the CRI (%) of the mixed coke was at 1100 ℃ and CO₂The weight loss rate when the coke was reacted for 2 hours under an atmosphere was determined.

Further, the gas utilization rate and the packed layer pressure loss under the above-described blast furnace raw material charging conditions were evaluated by the following procedures. The evaluation results are shown in Table 1.

[ gas utilization efficiency ]

Is defined as CO₂/(CO₂+ CO). times.100. CO used in the formula₂And the CO concentration (vol%) was measured using a movable gas distribution measuring device called a horizontal sensor (horizontal finder) from the center to the peripheral portion in the blast furnace.

[ pressure loss of filling layer ]

The total pressure loss of the blast furnace is divided by the amount of air blown, and the pressure loss of the raw material-packed bed (packed bed pressure loss) can be obtained by the following equation. Therefore, the packed bed pressure loss is considered to be an index of the air flow resistance required for the air flow per unit air volume.

Packed bed pressure loss (Δ P/V) ═ total pressure loss (kPa)/air delivery (Nm)³/min)

[ Table 1]

As is clear from table 1, when the inventive examples and the comparative examples are compared, the inventive examples are excellent in the packed bed pressure loss, and the reducing agent ratio, the air resistance index (packed bed pressure loss), and the gas utilization rate are improved.

As described above, it was confirmed that the reactivity in the blast furnace can be improved by mixing a large amount of coke having an appropriate particle size and good reactivity at an appropriate position in a position where the gas flow in the blast furnace is small.

Claims

charging coke in an amount of 25 to 80 mass% of the total coke amount in the primary charging into a blast furnace to form a coke layer, then, when a mixed raw material obtained by mixing the remaining coke in the primary charge and an ore-based raw material containing acid pellets, which is 10 mass% or more of the ore-based raw material in the primary charge, is loaded in 2 batches onto the coke layer, the particle diameter of the coke mixed in the 1 st batch is in the range of 15-40 mm, the 1 st batch is loaded into the range of the furnace mouth dimensionless radius of 0-0.8, the rest mixed raw material is loaded into the range of the furnace mouth dimensionless radius of 0.6-1.0 as the 2 nd batch, the reactivity index CRI of the coke mixed in the 1 st batch is in the range of 30-40%, and the amount of coke mixed in the 1 st batch is 60 to 80 mass% of the amount of coke mixed with the ore-based raw material.

2. The method of charging a blast furnace with a raw material according to claim 1, wherein a reactivity index CRI of the coke mixed in the 1 st batch is set to be 35% or more and 40% or less.

3. The method of charging a blast furnace with a raw material according to claim 1 or 2, wherein an amount of the coke mixed in the 1 st batch is 70 mass% or more and 80 mass% or less of an amount of the coke mixed with the ore-based raw material.