JP6303685B2 - How to charge the bellless blast furnace - Google Patents

Description

  The present invention relates to a charging method for a bell-less blast furnace. In particular, the present invention relates to a charging method for a bell-less blast furnace, which stabilizes the peripheral flow rising along the furnace wall of the blast furnace.

Due to the recent deterioration of resources, there is a demand for a wide variety of charges used in blast furnaces. In order to cope with this, development of a charge distribution control technology with higher accuracy than before is expected. In order to achieve the operation with high yield and low reducing material ratio, drastic improvement of air permeability in blast furnace is essential. In particular, charge distribution control is one of the important operating factors.
Recent large blast furnaces employ a swirl chute type (hereinafter referred to as bellless type) raw material charging device that has a swivel function at the top of the furnace and the elevation angle can be changed as a method for controlling the distribution of charges. doing. The raw material is charged in a ring shape by this chute.

As a bellless type raw material charging method, a two-batch charging method is generally known in which coke and ore are charged in this order in order to form a coke layer and an ore layer in a furnace.
However, in the 2-batch charging method, it is insufficient to ensure the central flow of the gas in the furnace, so as a method for improving the 2-batch charging method, the 3-batch charging method and the 4-batch charging method are used. Has been proposed.

The 3-batch charging method is a method in which a C batch of coke and an O batch of ore are charged in the order of C ₁ , C ₂ , O _{1 and} the like. Here, the C ₁ batch or C ₂ batches, a method for charging coke is employed in the furnace center portion. By forming the central coke layer, a certain in-furnace gas flow can be secured in the center of the furnace.

In the 4-batch charging method, C batch of coke and O batch of ore are ordered in the order of C ₁ , C ₂ , O ₁ , O ₂ , C ₁ , O ₁ , C ₂ , O ₂ , etc. It is a method of charging.
This 4 batch loading method, for example, first, in C ₁ batch, forming a horizontal terrace on the furnace wall side, an inclined coke layer which is inclined towards the furnace center of the furnace inside the horizontal terrace. Then, the C ₂ batches, charged coke to the furnace center. Next, in the O ₁ batch, ore is charged on the horizontal terrace or toward the boundary between the horizontal terrace and the inclined coke layer. Further, in the O ₂ batch, ore is charged in the furnace periphery on the horizontal terrace. Among these, in the O ₁ batch, the O / C distribution is adjusted by partially destroying the coke layer of the C ₁ batch with the charged ore.

As a four-batch charging method, it is described that the coke layer deposition shape is set to a coke terrace length of 0.3 or less and the inclination angle of the coke deposition layer is 10 ° to 20 ° during low coke operation (Patent Literature). 1).
However, the variation of raw materials stocks and water content of the coke to be charged, or the length of the horizontal terraces varies formed by C ₁ batch, there is a case where the deviation in the circumferential direction or cause. In such a case, there is a problem that the amount of coke collapse due to the O ₁ batch fluctuates and cannot be controlled to a desired O / C distribution.

On the other hand, it is practiced to mix fine-grained ore obtained by applying a sintered powder generated by a sieve under the blast furnace raw material tank on a secondary sieve into an ore batch and charging it into the periphery of the furnace.
For example, a particle-by-particle charging method has been proposed, which aims to improve gas flow distribution by individually charging sintered ore divided into fine particles of 1 mm to 5 mm and coarse particles of 5 mm to 18 mm into the furnace. (See Non-Patent Document 1).
In addition, using a recovery sieve equipped with a multi-stage inclined screen, fine-grained sintered ore of + 3mm size is efficiently classified, and fine-grained sintering is controlled by controlling the amount and position of fine-grained sinter into the furnace wall. A technique for recovering and using ores has been proposed (see Non-Patent Document 2).

JP 2008-208463 A

Yoshio Okuno, 5 others, "Improvement of all coke operation by charging method according to sinter particle size", Iron and Steel, Japan Iron and Steel Institute, 69th (1983) No. 14, P1578-P1584 Masaru Nakamura, 5 others, “Efficient recovery of fine-grained sintered ore and results of its use”, Iron and Steel, Japan Iron and Steel Institute, 72 (1986) No. 12, S875

When the method using the fine-grained sintered ore described in Non-Patent Documents 1 and 2 is applied to a 4-batch charging method or the like, it is conceivable that the ore batch is divided and charged. In this case, as an O ₂ batch, fine-grained sintered ore having a mass ratio of about 0.1 to 0.2 with respect to the total amount of ore to be charged is charged in the peripheral portion of the furnace wall. Before loading the granules sinter at such O ₂ batches, in C ₁ batch and O ₁ batch, it forms a terrace, it is conceivable to put a fine sintered ore thereon. However, due to the influence of the material brand discharged from the furnace top bunker and the time-series deviation of the particle size, the terrace length tends to have a circumferential deviation. Furthermore, the variation in the terrace length due to the coke layer causes the variation in the amount of coke collapse due to the ore charged in the O ₁ batch, and it is easy to promote local outgassing.

  In view of such a situation, the present invention aims to provide a charging method for a bell-less blast furnace that stabilizes the peripheral flow rising along the furnace wall of the blast furnace in four batch charging. To do.

The gist of the present invention is as follows.
(1) In the charging method of the bell-less blast furnace in which the C batch of coke and the O batch of ore are alternately charged in layers, the C ₁ batch is inclined downward from the furnace wall side toward the center of the furnace. The step of forming the inclined coke layer, the step of charging the C ₂ batch into the center of the furnace, and then charging the O ₁ batch toward the center from the furnace wall and substantially horizontal to the furnace wall side a horizontal terrace shape, further, forming a gradient ore layer which is inclined downwardly toward the center of the furnace from the furnace inner end of the horizontal terraces, finally, the O ₂ batches of the O ₁ batch 4 or 4 batches of C ₁ , C ₂ , O ₁ , and O ₂ that are carried out in the order of the process of charging on the horizontal terrace, and the O ₂ batch is over 3 mm and 6 mm or less from the center it becomes, and, from the furnace wall in the horizontal terraces of the O ₁ batch Length towards the, charge charging method bell-less blast furnace, characterized in that is less than 0.3 times 0.1 times or more relative to the furnace opening radius.

(2) The batches of C ₁ , C ₂ , O ₁ , and O _{2 in} the 4 batch charging are performed in the order of C ₁ , O ₁ , C ₂ , and O ₂ (1) The charging method of the bell-less blast furnace as described in 1.
(3) The method of charging a bellless blast furnace according to (1) or (2), wherein the O ₁ batch is a mixed batch of ore and small coke.

The figure which shows the apparatus structure until a raw material is charged into the furnace from the raw material tank in a bell-less blast furnace. The schematic diagram of the burden distribution of this embodiment. The figure which shows the raw material deposition profile in the actual furnace of Example 1. FIG. The figure which shows the raw material deposition profile in the actual furnace of the comparative example 1. FIG. The figure which shows the furnace condition change before and after application of each charging method in Example 1 and Comparative Example 1. FIG.

FIG. 1 is a diagram showing an apparatus configuration until a raw material is charged into a furnace from a raw material tank in a bell-less blast furnace. The apparatus configuration shown in FIG. 1 is an example of a direct charge system in which a surge hopper is not installed in the charging conveyor 3 and the cut ore and coke are directly charged into the furnace top bunker 7.
As shown in FIG. 1, the sintered ore stored in the raw material tank 15 is sieved with a primary sieve 2 having a mesh size of 6 mm below the raw material tank 15, and the sintered ore exceeding 6 mm on the sieve is sintered into the sintered ore tank. 1 recovered. On the other hand, the sintered ore under the sieve of the primary sieve 2 is put on the secondary sieve 4 having a mesh size of 3 mm. By this secondary sieve 4, the sintered ore exceeding 3 mm and not more than 6 mm on the sieve is recovered in the fine grain sintered ore tank 5 as fine grain sintered ore. In addition, the sintered ore of about 3 mm or less under the secondary sieve 4 is reused in the sintering plant. The sintered ore of the sintered ore tank 1 and the fine-grained sintered ore of the fine-grained sintered ore tank 5 are each a weighing hopper (not shown) attached to each of the sintered ore tank 1 and the fine-grained sintered ore tank 5. Weighed and discharged to charging conveyor 3 respectively.
The charged raw material 6 discharged from the charging conveyor 3 is temporarily stored in the furnace top bunker 7 and then the flow rate is controlled by adjusting the opening area of the discharge port 9 with the flow rate adjusting valve 8, while the collecting hopper 10 Then, the blast furnace 12 is charged via the turning chute 11. The charging raw material 6 is charged into the blast furnace furnace 12 while appropriately adjusting the inclination angle of the swivel chute 11 so that the charging raw material 6 is charged at a desired position.

FIG. 2 schematically shows the distribution of each charge in the coke layer and the ore layer in the 4-batch charging method in which C ₁ , C ₂ , O ₁ , and O ₂ are charged in this order. In this embodiment, the apparatus shown in FIG. 1 is used, and each batch of C ₁ , C ₂ , O ₁ , and O ₂ is charged so as to have the layer configuration shown in FIG.

In C ₁ batch, forming a gradient coke layer which is inclined downward toward the furnace wall side in the center of the furnace. As described above, the C ₁ batch is characterized in that coke is naturally deposited without forming a horizontal terrace by coke formed by the conventional 4-batch charging. Thus, only the inclined coke layer inclined downward from the furnace wall side toward the center of the furnace is formed.
This suppresses fluctuations in the length of the horizontal terrace and fluctuations in the circumferential direction caused by fluctuations in the raw material brand of the coke to be charged and the moisture content, which occurred in the conventional horizontal terrace of the coke layer. . As a result, when the subsequent O ₁ batch is charged, the amount of coke collapse is less likely to vary, so the O / C distribution can be controlled to be constant.

The C ₂ batches, charged coke in the center of the furnace. By forming the central coke layer, the central flow of the in-furnace gas is secured.

In the O ₁ batch, charging is performed from the furnace wall toward the center, and a horizontal terrace and an inclined ore layer having a substantially horizontal shape are formed on the furnace wall side.
In this O ₁ batch, it is preferable to use a mixed batch of ore and small coke. Such an ore / coke mixing method improves the air permeability and productivity of the ore layer by mixing coke with the ore, while at the same time bringing the ore and coke particles close to each other. This can improve the reducibility of the blast furnace and reduce the blast furnace fuel ratio. Therefore, by making O ₁ batch into a mixed batch of ore and small coke, the effect of ore / coke mixed charging can be exhibited together.
Further, the length from the furnace wall toward the center of the horizontal terrace of the O ₁ batch is formed so as to be 0.1 to 0.3 times the furnace port radius. If the O ₁ batch horizontal terrace has the above-mentioned length, it is possible to form a terrace that is large enough to allow fine-grained ore to stand in the O ₂ batch charging described later.

In the O ₂ batch, fine ore exceeding 3 mm and not more than 6 mm is charged on the horizontal terrace of the O ₁ batch. By this O ₂ batch, a layer of ore located on the furnace wall side is secured, and the peripheral flow rising along the furnace wall is controlled. Further, in the O ₂ batch, only the fine ore within the above range is charged. Therefore, the top bunker 7 generated when the mixed ore of the fine sinter and coarse sinter is used in the O ₂ batch. There is no time series deviation of the raw material brand charged into the furnace. For this reason, since the deviation in the circumferential direction does not occur in the distribution of the fine-grained ore charged on the furnace wall side, the occurrence of local outgassing can be suppressed. As described above, the peripheral flow rising along the furnace wall is stabilized, and as a result, stable operation is realized.
Furthermore, in the O ₂ batch charging, by leaving the fine ore still, the O ₂ batch of fine ore is loaded on the horizontal terrace of the O ₁ batch, and a fine ore layer is formed. Thus, fine ore layer of O ₂ batches, as well as the inclined ore layer O ₁ batch, a structure that is inclined downwardly toward the furnace wall side in the center of the furnace. For this reason, in the raw material deposition profile after charging the O ₂ batch, that is, the raw material deposition profile before charging the C ₁ batch of the next charge, an inclined layer inclined downward is formed from the furnace wall side to the center of the furnace. As a result, the horizontal terrace is not formed.

In the above embodiment, the example is described in which C ₁ , C ₂ , O ₁ , and O ₂ are performed in this order. However, each batch is performed in the order of C ₁ , O ₁ , C ₂ , and O _2. May be. In the 4-batch charging, the above effect can be achieved also in the order of C ₁ , O ₁ , C ₂ and O ₂ .
Moreover, in the said embodiment, although the mesh size of the primary sieve 2 was 6 mm and the mesh size of the secondary sieve 4 was 3 mm, you may change suitably according to the yield of a sintered ore. For example, the fine-grained sintered ore can be adjusted in particle size by adjusting the mesh sizes of the primary sieve 2 and the secondary sieve 4 within the range of 3 mm to 6 mm.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. In addition, this invention is not restrict | limited to the description content of these Examples at all.

[Example 1, Comparative Example 1]
The effect of the raw material charging method according to the present invention was verified by an actual furnace test for a blast furnace having a furnace volume of 3700 m ³ .
Example 1 is a raw material charging method according to the present invention. That is, in the C ₁ batch, towards the furnace wall side in the center of the furnace to form an inclined coke layer which is inclined downwardly, at the C ₂ batches, was charged with coke in the center of the furnace. Subsequently, in the O ₁ batch, the ore layer is charged from the furnace wall toward the center, the horizontal terrace is inclined to the furnace wall side, and the inclined ore layer is further inclined downward from the furnace inner end of the horizontal terrace toward the center of the furnace. Formed. In the O ₂ batch, fine ore was charged on the horizontal terrace of the O ₁ batch.
In the _{C 1} batch and _{C 2} batches of Example 1 were used coke particles径略30Mm～60mm. Further, in the _{O 1} batch, it was used a sintered ore of a particle size of about 6Mm～35mm, a mixed raw material obtained by mixing coke particles径略10Mm～40mm. As the O ₂ batch fine ore, a fine sintered ore of more than 3 mm and less than 6 mm produced by sieving was used.

Comparative Example 1 is a raw material charging method according to a conventional method. That is, in the C ₁ batch was charged towards the center from the furnace wall, a horizontal terrace on the furnace wall side, further inclined coke layer which slopes downwardly toward the furnace inner end of the horizontal terraces in the center of the furnace formed, with the C ₂ batches, it was charged with coke in the center of the furnace. Subsequently, in the O ₁ batch, the C ₁ batch was charged from the boundary between the horizontal terrace and the inclined coke layer toward the center. It was adjusted O / C ratio by breaking a part of the coke layer of C ₁ batch by the O ₁ batch charged. In the O ₂ batch, coarse ore was charged on the horizontal terrace of the O ₁ batch.
Incidentally, C ₁ batch of Comparative Example 1, coke and raw material mixture used in the C ₂ batches and O ₁ batch used was the same as in Example 1. As the O ₂ batch coarse ore, a sintered ore having a particle diameter of about 6 mm to 35 mm was used.

  The charging conditions according to the present invention as Example 1 are shown in Table 1 below, and the charging conditions according to the conventional method as Comparative Example 1 are shown in Table 2 below. The center of gravity of the relative drop position in Tables 1 and 2 is the center of gravity of the raw material drop position at the raw material charging level, where 0 is the furnace center and 1 is the furnace wall.

As shown in Table 2, in Comparative Example 1, 0.88 a relative drop position centroid _{C 1} batch was set to 0.77 in _{O 1} batch. In both of these, in order to form a horizontal terrace and maintain the formed horizontal terrace, the center of gravity of the relative fall position is located slightly away from the furnace wall.
On the other hand, as shown in Table 1, in Example 1, to a C ₁ batch does not form a horizontal terrace, a relative drop position centroid was 0.99. In the O ₁ batch, the relative drop position gravity center was set to 0.94 in order to form a small horizontal terrace for allowing the O ₂ batch of fine ore to settle. In addition, the O ₂ batch was charged only in the most peripheral part of the furnace having a relative gravity center of 1 for the fall position.

Next, the raw material deposition profile by each charging method of Example 1 and Comparative Example 1 was confirmed. FIG. 3 shows a raw material deposition profile in the actual furnace of Example 1. FIG. 4 shows a raw material deposition profile in the actual furnace of Comparative Example 1. In addition, the raw material deposition profile shown in FIG.3 and FIG.4 was measured with the profile meter.
Comparing FIG. 3 and FIG. 4, it can be confirmed that the raw material deposition profile is changing. Specifically, in the charging method of Comparative Example 1 shown in FIG. 4, a horizontal terrace (indicated by an arrow in FIG. 4) is formed after C ₁ batch charging and after O ₁ batch charging. ing. The horizontal terrace after the O ₁ batch was charged had a length from the furnace wall toward the center of 0.4 times the length of the furnace port radius (2 m from the furnace wall). On the other hand, in the charging method of Example 1 shown in FIG. 3, formation of a horizontal terrace is not recognized after C ₁ batch charging, and the length from the furnace wall toward the center after the subsequent O ₁ batch charging. However, a horizontal terrace (indicated by an arrow in FIG. 3) that is 0.25 times as large as the furnace port radius (1.25 m from the furnace wall) is formed. Then, after O ₂ batches charged, on the horizontal terraces, it can be confirmed that the fine ore layer is formed.

Next, the furnace state change before and after application of each charging method of Example 1 and Comparative Example 1 was confirmed. FIG. 5 shows changes in furnace conditions before and after application of each charging method in Example 1 and Comparative Example 1.
Specifically, first, the operation was performed by applying the charging method of Comparative Example 1, and then the operation was performed by changing the charging method and applying the charging method of Example 1. And at this time, by measuring and calculating the skin flow gas utilization rate and its standard deviation, skin flow temperature and its standard deviation, stave water supply and drainage temperature difference, the number of outgassing, and the amount of fine grain sinter used, respectively. The changes in furnace conditions before and after applying each charging method were confirmed. The skin flow gas utilization rate is expressed by the following equation (1) with respect to the component of the gas flowing in the nearest vicinity of the furnace, measured by a gas detector installed on the furnace wall located 21.335 m above the tuyere. This is the calculated ratio.
Gas utilization rate = {CO ₂ / (CO ₂ + CO)} × 100 (1)
Skin flow temperature is the temperature of the gas flowing in the nearest vicinity in the furnace, measured by a thermocouple installed on the furnace wall located 21.335 m above the tuyere. The stave water supply / drainage temperature difference is a difference between the water supply temperature of the cooling water flowing through the stave and the drainage temperature. The standard deviation of the skin flow gas utilization rate and the standard deviation of the skin flow temperature are standard deviations in eight circumferential directions.

As shown in FIG. 5, when the charging method of Comparative Example 1 was applied, local gas escape from the periphery of the furnace was sporadic, and the gas flow nearest to the furnace was unstable.
In addition, when the charging method of Comparative Example 1 is applied, the gas utilization rate in the vicinity of the furnace is as low as about 40%, and the skin flow temperature is also increased as high as 350 to 400 ° C. Since it is as high as around 10 ° C., it can be seen that the flow rate of gas flowing in the nearest vicinity in the furnace is large, and the furnace body heat load is high. Furthermore, both the skin flow gas utilization rate and the skin flow temperature had large standard deviations and large fluctuations.
On the other hand, when the charging method of Example 1 was applied, the number of outgassing was reduced to almost 0, the gas utilization rate of the skin flow was improved to about 45%, and the skin flow temperature was reduced to about 300 ° C. Further, since the temperature difference between the stave water supply and drainage is as small as 6 to 8 ° C., it can be seen that the flow velocity of the gas flowing in the nearest vicinity in the furnace is small and the furnace heat load is reduced. In addition, the standard deviation of the skin flow gas utilization rate and the standard deviation of the skin flow temperature were both reduced and the fluctuations were reduced, so that fluctuations in the peripheral flow rising along the furnace wall were suppressed. Can be confirmed.

  The present invention can be used as a charging method for a bell-less blast furnace that can stabilize the gas flow in the furnace near the wall of the blast furnace.

  DESCRIPTION OF SYMBOLS 1 ... Sintering ore tank, 2 ... Primary sieve, 3 ... Charge conveyor, 4 ... Secondary sieve, 5 ... Fine grain sintered ore tank, 6 ... Raw material for charging, 7 ... Top bunker, 8 ... Flow control valve , 9 ... Discharge port, 10 ... Collecting hopper, 11 ... Revolving chute, 12 ... Inside the blast furnace, 15 ... Raw material tank.

Claims (3)

In the charging method of the bell-less blast furnace in which C batch of coke and O batch of ore are alternately charged in layers,
Forming a slanted coke layer in which C ₁ batch is inclined downward from the furnace wall side toward the center of the furnace;
The C ₂ batches, the step of loading in the center of the furnace,
Next, the O ₁ batch is charged from the furnace wall toward the center, a horizontal terrace having a substantially horizontal shape on the furnace wall side, and further downward from the inner tip of the horizontal terrace toward the center of the furnace. Forming an inclined ore layer inclined to
Finally, the _{O 2} batches, a 4 batches charging of _{C 1,} C _2, O 1, _{O 2} to be carried out in the order of the step of loading on the horizontal terraces of the _{O 1} batch,
The O ₂ batch is made of fine ore of more than 3 mm and not more than 6 mm, and the length of the O ₁ batch from the furnace wall to the center of the horizontal terrace is 0.1 times or more with respect to the furnace port radius A charging method for a bell-less blast furnace, which is 0.3 times or less. The respective batches of C ₁ , C ₂ , O ₁ , and O _{2 in} the 4-batch charging are performed in the order of C ₁ , O ₁ , C ₂ , and O ₂ , How to charge the bellless blast furnace. The method for charging a bell-less blast furnace according to claim 1 or 2, wherein the O ₁ batch is a mixed batch of ore and small coke.

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