JP6041073B1 - Raw material charging method to blast furnace - Google Patents

Abstract

We propose a method for charging raw materials into a blast furnace that can ensure the air permeability in the blast furnace and stabilize the blast furnace operation and improve the thermal efficiency. When charging the raw material mixed with ore raw material and coke into the blast furnace via the swivel chute, the swirl chute is inclined at an average angle θ1 with respect to the axial direction of the blast furnace, A coke having a particle size 1.1 to 3.0 times the particle size of coke to be fed and then tilted at an average angle θ2 larger than the average angle θ1 and mixed with the charged raw material O1. The mixed charging raw material O2 is supplied to form a raw material charging layer.

Description

  The present invention relates to a raw material charging method into a blast furnace, in which the raw material is charged into a blast furnace through a turning chute.

  A blast furnace is generally charged with ore raw materials such as sintered ore, pellets, and massive ore and coke stacked in the direction of the furnace axis from the top of the blast furnace, and combustion gas is allowed to flow from the tuyere of the blast furnace. It is a facility for burning pigs and obtaining pig iron from ore. Coke and ore raw materials, which are blast furnace charging materials charged in the blast furnace, descend from the top of the furnace to the lower part of the furnace, and ore reduction and raw material temperature rise occur. The ore raw material layer gradually deforms while filling the gaps between the ore raw materials due to the temperature rise and the load from above, and under the shaft part of the blast furnace, it has a very high ventilation resistance and a gas that hardly flows. Form a layer.

Conventionally, raw material charging into a blast furnace is performed by alternately charging ore raw materials and coke, and in the furnace, ore raw material layers and coke layers are alternately layered. Further, in the lower part of the blast furnace, there are an ore raw material layer having a high air flow resistance in which ores are softened and fused, and a coke slit derived from coke and having a relatively low air resistance.
The air permeability of this cohesive zone has a great influence on the air permeability of the entire blast furnace, and the productivity in the blast furnace is limited. When performing low coke operation, which suppresses the use of coke, the amount of coke used is reduced, so the coke slit can be considered as thin as possible, and it is important to ensure the permeability of the cohesive zone. become.

  In order to improve the permeability of the cohesive zone, it is known that mixing coke with the ore raw material layer is effective. Therefore, many studies have been made to obtain an appropriate mixed state of coke. For example, in Patent Document 1, in a bell-less blast furnace, coke is charged into the ore hopper on the downstream side of the ore hopper, and the coke is stacked on the ore on the conveyor, and then charged into the furnace top bunker. The ore and coke are charged into the blast furnace through the turning chute.

  In Patent Document 2, ore and coke are separately stored in a bunker at the top of the furnace, and coke and ore are mixed and charged at the same time, so that a normal charging batch for coke and a central charging batch for coke are used. And three batches for mixing and charging are performed simultaneously.

  Further, in Patent Document 3, in order to prevent the destabilization of the cohesive zone shape in the blast furnace operation and the decrease in the gas utilization rate near the center, and to improve the safe operation and the thermal efficiency, In addition, all ore and all coke are thoroughly mixed and then charged into the furnace.

JP-A-3-211210 JP 2004-107794 A Japanese Patent Publication No.59-10402

By the way, in order to improve the ventilation resistance of the cohesive zone, it is effective to mix coke in the ore layer as in the technique described in Patent Document 3 described above.
However, the average particle size of the typical coke described in Patent Document 3 is about 40 mm and the average particle size of the ore is about 15 mm, and the particle sizes of both are greatly different. Ore gets in between, the porosity is greatly reduced, the air permeability is deteriorated in the furnace, and there is a possibility that troubles such as blowout of gas and poor lowering of raw materials may occur.

  In order to avoid these troubles, a method of forming a coke-only layer in the furnace axis can be considered. According to this method, the passage of gas through the coke layer is secured in the core portion of the furnace, so that air permeability can be improved.

  However, when performing operation with a large amount of pulverized coal blown from the tuyere as a blast furnace reducing material, air permeability is increased due to an increase in the amount of unburned pulverized coal and the Ore / Coke ratio (mass ratio of ore and coke). In particular, the air permeability around the furnace wall is greatly deteriorated, and even if the air permeability is ensured only in the core part of the furnace, it cannot be said that the air permeability of the entire furnace is sufficient. In addition, when performing the low coke operation as described above, the formation of the coke layer itself in the core part of the furnace may be insufficient.

  The present invention has been developed in view of the above situation, and ensures air permeability in the blast furnace even when the amount of coke is small or when a large amount of pulverized coal is injected. Thus, an object of the present invention is to propose a raw material charging method for a blast furnace which can achieve stabilization of blast furnace operation and improvement of thermal efficiency.

但し、θk,iはｉ周目の旋回シュートの高炉の軸方向に対する角度であり、ｋ＝１がθ１およびｋ＝２がθ２をそれぞれ示している。That is, the gist configuration of the present invention is as follows.
1. When charging the raw material mixed with ore raw material and coke into the blast furnace via the swivel chute,
The swirling chute is tilted at an average angle θ1 with respect to the axial direction of the blast furnace to supply the charging raw material O1, and then the swirling chute is tilted at an average angle θ2 larger than the average angle θ1 to inject the charging raw material. A raw material charging method into a blast furnace in which a raw material charging layer is formed by supplying a charging raw material O2 mixed with coke having a particle size 1.1 to 3.0 times the particle size of coke mixed with O1.
Here, the ore raw material is a general term for sintered ore, pellets, massive ore, and the like. The average angle is defined by the following equation.

Here, θk, i is the angle of the turning chute of the i-th rotation with respect to the axial direction of the blast furnace, k = 1 indicates θ1, and k = 2 indicates θ2.

  In the above 1, the formation of the raw material charging layer is defined, but the blast furnace operation is performed by alternately stacking the coke layer and the charging raw material layer in the entire blast furnace. Furthermore, a coke layer extending in the axial direction may be formed at the center of the blast furnace.

2. 2. The raw material charging method to the blast furnace as described in 1 above, wherein a particle size of coke mixed with the charging raw material O2 is 1.5 times or more of a particle size of coke mixed with the charging raw material O1.

3. 3. The raw material to the blast furnace according to 1 or 2 above, wherein the particle size of coke mixed with the charging raw material O1 is 0.5 to 1.5 times the particle size of the ore raw material mixed with the charging raw material O1. The charging method.

  According to the present invention, even in an operation with a low coke amount and an operation with a large amount of pulverized coal injection, the air permeability in the blast furnace can be reliably ensured, thereby realizing a stable blast furnace operation with high thermal efficiency. Is done.

It is a schematic diagram which shows the blast furnace of a turning chute system. It is a schematic diagram which shows the conventional raw material charging state. It is a schematic diagram which shows the raw material charging state according to this invention.

Hereinafter, the present invention will be specifically described.
An example in which the raw material charging method of the present invention is applied to an actual turning chute blast furnace will be described with reference to FIGS.
In FIG. 1, reference numeral 1 is a blast furnace, 2 is a blast furnace throat, 3 is a blast furnace belly, 4a to 4c are furnace bunker, 5 is a coke layer, 5a is a central coke layer, 5b is a peripheral coke layer, and 6 is an ore. A raw material layer in which a raw material and coke are mixed, 7 is a collecting hopper, 8 is a bell-less charging device, 9 is a swivel chute, and 10 is a tuyered air duct.
In this example, only the coke is stored in the furnace top bunkers 4a and 4b, and only the ore raw material is stored in the furnace top bunker 4c. Further, cokes having different particle diameters are stored in 4a and 4b charged with only coke. And it cuts out simultaneously from the furnace top bunker 4a and 4c, and similarly cuts out simultaneously from the furnace top bunker 4b and 4c, and mixes and supplies an ore raw material and coke. The method for forming the mixed layer having different coke particle diameters is not limited to the above. For example, a furnace top bunker is prepared by placing a mixture of ore raw materials and coke in advance on a conveyor that transports raw materials to the furnace top bunker. And the mixture may be supplied from one top bunker.

The raw material charging in the swirl chute blast furnace is performed by alternately charging the raw material and coke with the swirl chute 9, and the coke layer 5 and the charging raw material layer 6 are alternately layered in the furnace. To deposit.
Here, as a specific example of the charging procedure of the coke layer, as shown in FIG. 2, first, the raw material charging destination of the turning chute 9 is set as the inner peripheral portion of the furnace wall of the blast furnace 1 by a so-called forward tilting method. The coke is charged from the furnace top bunker 4a or 4b charged with only coke, thereby forming the peripheral coke layer 5b on the inner peripheral portion of the furnace wall. Next, the coke is charged from the furnace top bunker 4a or 4b with the raw material charging destination of the swivel chute 9 as the axial center of the blast furnace, thereby forming the central coke layer 5a in the axial center of the blast furnace.
On the coke layer 5 thus formed, the charging raw material layer 6 is stacked and formed. Previously, as shown in FIG. 2, a single charging material layer 6 was formed.

  On the other hand, in this invention, as shown in FIG. 3, the charging raw material which mixed the ore raw material from the furnace top bunker 4c and the small particle size coke from the furnace top bunker 4a by cutting out simultaneously. O1 is supplied to the core side to form the inner charging raw material layer 6a. Furthermore, the raw material O2 mixed from the ore raw material from the furnace top bunker 4c and the coke having a larger particle size than the coke of the raw material O1 from the furnace top bunker 4b is mixed on the furnace wall side. The outer charging material layer 6b is formed by supplying. The charging raw material layer 6 is constituted by the lamination of the inner charging raw material layer 6a and the outer charging raw material layer 6b. At that time, it is important that the ratio DpC2 / DpC1 of the particle size DpC2 of the coke mixed with the charging raw material O2 and the particle size DpC1 of the coke mixed with the charging raw material O1 is 1.1 to 3.0. is there.

That is, as shown in FIG. 1, when the angle of the turning chute 9 with respect to the axis L of the blast furnace is θ, first, the charging chute 9 is inclined at an average angle θ1 and the charging material O1 is supplied to the core side to The charging raw material layer 6a is formed. Next, the turning chute 9 is tilted at an average angle θ2 larger than the average angle θ1, and the charging raw material O2 having a large mixed coke particle size is supplied to form the outer charging raw material layer 6b.
Here, the average angles θ1 and θ2 of the turning chute 9 are preferably set to θ2 / θ1 of 1.1 to 2.0 from the viewpoint of ensuring the air permeability and reactivity of the charging raw material layer.

By arranging the charging raw material layers 6 laminated as described above alternately with the coke layers 5, the air permeability in the blast furnace can be reliably ensured. This is because the gas flow rate in the blast furnace is not uniform from the center of the furnace to the furnace wall and has a distribution, so that the permeability can be secured by charging coke with different particle sizes. That is, since the gas easily flows through the furnace wall portion in the shortest path connecting the blast furnace tuyere and the furnace mouth, coke having a large particle size with good air permeability is charged so as not to inhibit the gas flow.
In particular, by setting the ratio DpC2 / DpC1 between the particle size DpC2 of coke mixed with the charging raw material O2 and the particle size DpC1 of coke mixed with the charging raw material O1 to 1.1 to 3.0, The charged raw material O1 is deposited and mixed with highly reactive small particle size coke in order to ensure the reducibility of the ore, while the charged raw material O2 is aerated to improve the air permeability. Coke having a small particle size and a small resistance is deposited and mixed, so that reducibility and air permeability can be achieved at a high level.

  That is, when the ratio DpC2 / DpC1 is less than 1.1, coke having a small airflow resistance and a large particle size cannot be deposited and mixed, so that the effect of improving air permeability cannot be obtained. Preferably, it is 1.5 or more. On the other hand, when the ratio DpC2 / DpC1 exceeds 3.0, the airflow resistance is reduced, but the reactivity is further reduced, and thus the effect of improving the reduction cannot be obtained. Preferably, it is 2.0 or less.

Furthermore, it is preferable that the ratio DpC1 / DpO1 of the particle diameter DpC1 of the coke mixed with the charging raw material O1 to the particle diameter DpO1 of the ore raw material mixed with the charging raw material O1 is 0.5 to 1.5.
That is, if the ratio DpC1 / DpO1 is less than 0.5, coke with a small particle size is mixed in the vicinity of the furnace center, and the ventilation resistance becomes high, which may hinder the gas flow flowing in the vicinity of the center of the blast furnace. is there. On the other hand, when the ratio DpC1 / DpO1 exceeds 1.5, the reactivity of the charged raw material O1 disposed on the core side becomes small, and it becomes difficult to obtain the effect of improving the reducing property. More preferably, it is 1.0 to 1.2.

In the actual blast furnace of the swirl chute system shown in FIG. 1, the same mixing ratio of coke mixed with the ore raw material is made the same, and then DpC2 / DpC1 in the charging raw materials O1 and O2, and the charging raw material O1. As shown in Table 1, charging raw materials O1 and O2 having various changes in DpC1 / DpO1 in FIG. , Performed each operation. The operational results in each case were investigated. The survey results are also shown in Table 1.
Here, the output ratio is a value obtained by dividing the daily output (t / d) of the blast furnace by the furnace volume (m ³ ). The reducing material ratio, the coke ratio, and the pulverized coal ratio are the amount of reducing material, the amount of coke, and the amount of pulverized coal (kg / t) used when producing hot metal 1t.

  As shown in Table 1, Inventive Examples 1 to 9 have a coke ratio in the range of 339 to 353 kg / t, and have a low coke ratio as compared with the coke ratio of Comparative Examples 1 to 3 in the range of 356 to 360 kg / t. Yes. However, even in such an operation with a low coke ratio, ΔP / V, which is an index of ventilation resistance, is 18.3 to 20 lower than the range of 20.9 to 23.1 in Comparative Examples 1 to 3. .8 range.

1 Blast Furnace 2 Blast Furnace Furnace 3 Blast Furnace Abdomen 4a-4c Top Bunker 5 Coke Layer 5a Central Coke Layer 5b Peripheral Coke Layer 6 Charge Raw Material Layer 6a Inner Charge Raw Material Layer 6b Outer Charge Raw Material Layer 7 Collecting Hopper 8 Bellless Type charging device 9 swivel chute 10 tuyere air duct

Claims (2)

When charging the raw material mixed with ore raw material and coke into the blast furnace via the swivel chute,
The orbital raw material and coke having a particle size of 0.5 to 1.2 times the particle size of the ore raw material are mixed by tilting the turning chute at an average angle θ1 with respect to the axial direction of the blast furnace. that instrumentation supplying the incoming raw material O1, and then tilting the swivel chute at the average angle θ1 larger average angle .theta.2, the instrumentation same ore material and the ore material to be mixed in the incoming raw material O1, the charging material charging of the charging material O2 which coke Ru is mixed with a particle size of 1.1 to 2.0 times the particle size of the coke to be mixed with the raw material O1 is supplied to the blast furnace to form a raw material sintering bed Method.   The method of charging a raw material into a blast furnace according to claim 1, wherein the particle size of coke mixed with the charged raw material O2 is 1.5 times or more than the particle size of coke mixed with the charged raw material O1.

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