JP2008024997A - Method for charging material to be charged into bell-less blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for charging a material to be charged into a bell-less blast furnace with which gas permeability in a fused zone range at the lowest part of the furnace is improved and the stable operation of the blast furnace can be obtained by stabilizing the flowing of the gas in the furnace. <P>SOLUTION: The method for charging the material to be charged is performed as the followings, with which ore is divided into two or more of batches and small block cokes having 5-40mm granular diameter are mixed in each batch dividing the charged ores and the small block coke mixing quantity in the ore first batch is made to be larger than the small block coke mixing quantity on and after the second batch and also, the materials are charged from the furnace wall side toward the furnace center part. Further, in the case of setting X for distance in the furnace radius direction between the piling position in the furnace after charging the small block coke mixed in the ore into the blast furnace and the furnace wall and R for radius of the furnace opening hole in the blast furnace, it is desirable to charge the charging material so that the distance between the piling position of the small block coke and the furnace wall, and the radius of the furnace opening hole satisfies the relation of X/R≤0.3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging method of a charge in a blast furnace, and more particularly, in a bell-less blast furnace having a furnace bunker and a distribution chute at the top of the blast furnace and mixing a small coke with the ore and a small lump in the furnace. The present invention relates to a charging method for adjusting a coke accumulation position.

  In blast furnace operation, coke as a reducing material and sintered ore, pellets, lump ore, etc. as iron sources (hereinafter these iron sources are collectively referred to as “ores”) are generally charged alternately from the top of the furnace. Then, hot air is blown from the tuyeres at the bottom of the furnace, and pulverized coal or tar is blown.

  In order to maintain the stable operation of the blast furnace, it is necessary to ensure good air permeability and to stabilize the gas flow in the furnace, that is, to secure a stable center gas flow and furnace wall gas flow. The air permeability in the blast furnace is greatly affected by the properties, grain size, and amount of charged coke and ore (hereinafter also referred to as “charge”). It is also greatly affected by the method of charging the object, for example, the distribution of the charge charged in the furnace.

  As a method of improving the air permeability in the blast furnace, the cohesive zone formed in the lower part of the blast furnace by mixing and charging small coke into the ore layer (the region where the ore layer is softened and fused) It is known that breathability can be improved. For this reason, many mixing methods of ore and coke aiming at improving the air permeability of the cohesive zone in a blast furnace are disclosed.

  For example, in Patent Document 1, coke is charged into a plurality of ore hoppers on the downstream side of the ore hopper group, and discharge of coke is started within 10% of the total amount of ore on the ore cutting conveyor. Coke is stacked on the top of 30% or more of the total amount of the layer, and the stacked ore and coke are charged into the ore cutting hopper, and the ore and coke cut from the ore cutting hopper are loaded into the furnace bunker. A raw material charging method in a bell-less blast furnace is disclosed in which ore and coke discharged from a top bunker are charged into a blast furnace through a turning chute. This method aims to make the ratio of coke in the ore uniform in the radial direction in the furnace.

  However, since the air permeability in the blast furnace is greatly affected by the air flow resistance of the charge in the furnace wall, the air permeability is improved rather than uniformly charging the mixture of ore and coke in the radial direction of the furnace. Distributing and charging in high-efficiency parts has a remarkable effect in improving the reduction efficiency in the furnace and improving the air permeability.

  Patent Document 2 describes the gas flow distribution and temperature distribution in the vicinity of the furnace wall by charging small coke with a particle size of 5 to 30 mm directly above the ore layer in the range of 500 mm from the furnace wall of the blast furnace. A blast furnace operating method is disclosed that regulates and prevents the formation of furnace wall deposits. However, since the blast furnace has a different radii depending on the furnace volume, the relative position of the small coke in the radial direction of the furnace depends on the size of the blast furnace radii. Is different. Therefore, this method is not applicable to all blast furnaces. In the case of a large blast furnace, some small coke may flow into the center of the furnace and hinder the center flow.

  Furthermore, in Patent Document 3, the raw materials for both coke and ore are divided into two or more according to particle size, and fine particles are mixed with fine particles, and coarse particles are mixed with coarse particles. However, a method is disclosed in which a coarse mixture is charged in the center and middle regions of the furnace and a fine mixture is charged in the region of the furnace wall.

  However, in the method disclosed in Patent Document 3, since raw materials obtained by mixing fine raw materials are charged into the region of the furnace wall portion, the raw material with extremely small particle size concentrates on the furnace wall portion. It is expected that the air permeability of the inside will deteriorate significantly. Therefore, when this method is carried out, it is expected that the amount of the small coke used and the effect thereof are limited.

  On the other hand, in recent blast furnace operation methods, a multi-batch charging method is becoming mainstream for the purpose of improving the distribution controllability of the blast furnace charge. In the multi-batch charging method, as charging of one charge (referred to as one charge), each charge is divided into a plurality of batches and charged into the furnace. This is a charging method for forming a plurality of ore layers.

  For example, when ore is divided into two batches and charged into the furnace as one charge, two ore layers are formed in the furnace. Among the multi-batch charging methods, in particular, the batching of ore batches is a charging method suitable for improving the air permeability in the furnace by effectively utilizing the coke collapse phenomenon in the furnace, Since it is a charging method suitable for increasing the amount of fine-grained charge, it is an indispensable charging method in a bell-less blast furnace.

  For example, Patent Document 4 discloses a blast furnace operation method in which medium and small-sized coke having a particle size of 5 to 40 mm is mixed from an intermediate portion in the radial direction of the furnace into a peripheral ore layer. Disclosed is a method of charging in small batches to form two ore layers in the furnace, and mixing small or large coke into the ore in the peripheral part from the intermediate part in the furnace radial direction of one of the ore layers ing.

  However, since the method disclosed in Patent Document 4 is a method in which the ore is divided into two batches and the medium and small coke is mixed only in one of the batches, the ore charged from the batch that does not mix the medium and small coke. In the layer, there is a problem that the effect of mixing small and medium coke cannot be obtained.

  Further, in Patent Document 5, in a method of operating a blast furnace in which a charge is charged from a furnace center toward a furnace wall, ore is divided into two or more batches, and one divided batch is divided into small coke. A blast furnace operating method is disclosed in which a smooth and stable operation is possible by charging the mixed batch into a furnace wall portion. However, in the method disclosed in Patent Document 5, since charging is performed from the furnace center toward the furnace wall, mixing of the small coke and the ore is not promoted, and as a result, charging of the small coke is not performed. There is a problem that it is limited to the charging to the furnace wall.

  In order to solve these problems, the present applicant, in Patent Document 6, as a method of charging ore into two or more batches, a small coke is added to each divided batch of ores to be charged. A charging method for charging a bellless blast furnace was proposed, characterized in that the mixing amount of the small coke after the second ore batch is larger than the mixing amount of the small coke in the first ore batch. By this method, the mixing amount of the small coke and the charging position in the furnace were optimized, and the problem that the effect of mixing the small coke was not sufficiently exhibited was solved.

  As described above, the method proposed in Patent Document 6 maximizes the effect of mixing the small coke to improve the air permeability in the lower cohesive zone region, stabilize the gas flow in the furnace, and improve the bellless blast furnace. It is an excellent charging method that can achieve stable operation. However, in the charging method proposed in Patent Document 6, when the heat load on the furnace wall is high, for example, due to the distribution state in the radial direction of the furnace interior charge, the furnace wall side is more than the center side. It has been found that there is room for further improvement when the ventilation is good and the air from the tuyeres flows from the center side to the furnace wall side.

  That is, in the method proposed in Patent Document 6, the amount of small coke mixed after the ore second batch is used more than the amount of small coke mixed in the ore first batch, so that the cohesive zone close to the furnace wall is used. A situation occurs in which the effect of improving air permeability becomes excessive. For this reason, since the gas flow on the furnace wall side becomes stronger than the cohesive zone, it was confirmed that the heat load on the furnace wall further increased.

Japanese Patent No. 2820478 (claims and page 2 left column 40 lines to right column 2 lines) JP-A-8-239705 (Claims and paragraph [0006]) JP 63-140006 (Claims and page 2, lower right column, lines 2 to 15) JP 2002-3910 (Claims and paragraph [0020]) Japanese Patent No. 3700457 (Claims and paragraph [0010]) JP 2005-290511 A (Claims and paragraph [0023])

  As mentioned above, in order to ensure stable operation of the blast furnace, it is essential to increase the efficiency of ore reduction in the blast furnace and maintain good air permeability in the cohesive zone at the bottom of the furnace. It is effective to mix the small coke with the.

  However, even if the method of mixing the small coke in the ore layer is employed, there is a problem that the effect is not sufficiently exhibited depending on the mixing method of the small coke and the charging position in the furnace. Furthermore, when the heat load on the furnace wall is high, if the effect of improving the air permeability of the cohesive zone near the furnace wall side becomes excessive, the gas flow on the furnace wall side becomes stronger than the cohesive zone, There is also a problem that the heat load on the furnace wall further increases.

  The present invention relates to a method of charging ore into two or more batches, in which the effect of mixing and charging the small coke charged into each batch is maximized, so It is an object of the present invention to provide a charging method for a bell-less blast furnace that can improve the air permeability in the region, stabilize the gas flow in the furnace, and achieve stable operation of the blast furnace.

In order to solve the above-mentioned problems, the present inventor mainly conducted a heating load softening test up to a high temperature simulated based on the temperature in the blast furnace, the gas composition, and the charging load condition based on the conventional problems. Various studies were made. As a result, the knowledge shown in the following (a) to (d) was obtained.
(A) When ores are divided into two or more batches (two or more layers are formed after entering the furnace interior), and when the small batch coke is mixed into the divided batches and charged into the blast furnace, When small coke is mixed in the layer, the reduction reaction of the ore proceeds more quickly and the air permeability becomes better than when small coke is mixed only in a specific ore layer. (Meaning the value obtained by integrating the pressure loss of gas in the coke and ore packed bed over the temperature rise test temperature) is improved.
(B) When the charge is charged from the furnace wall side toward the furnace center, small coke flows along the uppermost surface of the furnace interior charge accumulation layer, that is, along the inclined surface of the stock level. Since it becomes possible to promote mixing of the lump coke and the ore, the reduction reaction of the ore proceeds more rapidly, and the high temperature load softening property is also improved.
(C) It is desirable that the deposition position after charging the small coke mixed with the ore is an area within 30% of the furnace port radius from the furnace wall. When the deposition position becomes larger than 30% of the furnace port radius from the furnace wall, the small coke flowing along the inclined surface of the stock level reaches the center of the furnace and occupies a large ratio to the cross-sectional area of the blast furnace. This is because the effect of improving the air permeability of the cohesive zone in the furnace wall portion is reduced.
(D) Control of the gas flow in the furnace wall becomes easier by increasing the mixing amount of the small coke in the first ore batch than in the second ore batch or later. The reason for this is that when the heat load on the furnace wall is high, the effect of improving the air permeability of the cohesive zone close to the furnace wall part becomes excessive by increasing the small coke after the second batch of ore. Therefore, a large amount of small coke is charged into the first batch of ore, and a mixed layer of ore and small coke is formed within an area within 30% of the furnace port radius from the furnace wall. This is because the gas permeability of the partial cohesive zone is improved and the gas flow can be easily controlled.

The present invention has been completed on the basis of the above findings, and the gist thereof is the method of charging the charged material into the bell-less blast furnace shown in the following (1) and (2).
(1) A charge charging method for a bell-less blast furnace in which ore is divided and charged into two or more batches, each of which is divided into small batches having a particle size of 5 to 40 mm. Mix coke and make the amount of small coke mixed in the first batch of ore larger than the amount of small coke mixed in the second batch of ore and charge from the furnace wall side toward the furnace center. Charging method for the bell-less blast furnace characterized by
(2) Small coke mixed with ore, where X is the distance in the furnace radial direction between the deposition position and the furnace wall after entering the blast furnace interior, and R is the blast furnace radius of the blast furnace. The method of charging a bell-less blast furnace according to (1), wherein the distance between the deposition position and the furnace wall and the radius of the furnace port satisfy the relationship represented by the following expression (1).
X / R ≦ 0.3 (1)
In the present invention, “loading the charge from the furnace wall side toward the furnace center” means that the distribution chute is rotated while its inclination angle (angle formed between the longitudinal direction of the distribution chute and the vertical line). Means that the charge is charged in a spiral or multiple ring shape from the furnace wall side toward the furnace center.

  In addition, “position of small coke mixed with ore in the furnace after entering the blast furnace interior” means that after the small coke mixed in each batch of ore is charged into the blast furnace, It means the position in the furnace radial direction deposited on the level surface.

  According to the charging method of the bellless blast furnace according to the present invention, the ore is divided into two or more batches, and the mixing amount of the small coke into each batch and the charging position of the small coke into the furnace are determined. By optimizing, the effect of mixing the small coke can be maximized to improve the air permeability in the cohesive zone of the lower part of the furnace, and the stable operation of the blast furnace can be ensured by ensuring a stable gas flow in the furnace. it can.

  Further, even when the heat load on the furnace wall is high, further increase in the heat load on the furnace wall can be suppressed while improving the air permeability of the fusion zone near the furnace wall.

The charge charging method to the bell-less blast furnace of the present invention is a method of charging ore into two or more batches, and the particle size is 5 to 40 mm in each batch of the ore to be charged. The amount of small coke mixed in the first ore batch is made larger than the amount of small coke mixed in the second or subsequent batch of ore and the charge is charged from the furnace wall toward the furnace center. It is characterized by entering. The reason why the present invention is limited to the above range and the preferable range will be described below.
(1) Charging the charge from the furnace wall side to the furnace center side By charging the charge from the furnace wall side to the furnace center, small coke and ore using the stock level inclination This is because the mixing with is promoted. As described above, when the mixing of the small coke and the ore is promoted, the reduction reaction of the ore proceeds more rapidly, and the air permeability improvement effect of the cohesive zone is more remarkably exhibited.
(2) Mixing a larger amount of small coke in the first batch than in the second batch of ore The reason for mixing small coke in each batch of ore is that small coke is mixed in the ore layer of each batch. This is because the contact area between the block coke and the ore increases, and the reduction proceeds efficiently by the reducing gas rising in the furnace.

  However, when the heat load on the furnace wall is high, if the effect of improving the air permeability of the cohesive zone near the furnace wall becomes excessive, the gas flow on the furnace wall side becomes stronger than the cohesive zone, There is also a problem that the heat load on the furnace wall further increases.

  For this reason, in the charging method of the present invention, when the ore is divided into two or more batches and charged, the small coke mixing ratio in the ore in the first batch is changed to the ore in the second batch and thereafter. The effect of improving the air permeability of the cohesive zone was optimized by increasing the mixing ratio of the small coke in the layer. The reason why the air permeability improvement effect is optimized by mixing a larger amount of small coke in the first batch than in the second ore batch or more is as follows.

  When the ore layer of the first batch is charged on the coke layer, mixing of the coke layer and the ore layer proceeds due to the effect of slope classification. On the other hand, the ore layer after the second batch is hardly mixed with coke.

  In the charging method according to the present invention, a large amount of small coke is mixed in the ore layer of the first batch, so that contact between the coke and the ore can be further increased, and the reduction of the ore can proceed rapidly. it can.

That is, it is not necessary to mix a large amount of small coke in the ore layer after the second batch in order to proceed the reduction of the ore quickly, so the effect of improving the permeability of the cohesive zone close to the furnace wall side is achieved. It is because it does not become excessive.
(3) Particle size of small coke 5-40mm
The reason why a small coke having a particle size of 5 to 40 mm is used is that if the particle size is within this range, the reduction reaction with the ore is efficiently performed while descending the blast furnace, and as the small coke, This is because the necessary amount can be secured.
(4) The ratio of the radial position distance between the deposition position of the small coke after entering the furnace interior and the furnace wall, the value of (X / R) is 0.3 or less The value of the ratio (X / R) is 0.3 The following is preferable. When the value of the ratio is 0.3 or less, even when charging the charge from the furnace wall side toward the furnace center, small coke flows into the furnace center along the stock level inclined surface. This is because the air permeability improving effect of the cohesive zone is exhibited.

In order to confirm the effect of the charging method of the present invention, a test operation was performed in a blast furnace having a furnace internal volume of 5370 m ³ and the results were evaluated. The test operation is based on the following conditions: output ratio: 2.1 t / d / m ³ , (Ore / Coke) ratio: 4.4, pulverized coal injection amount: 120 kg / t-pig, coke base: 31 t The operation was continued for 5 days under the same operating conditions, and then the operation was shifted to the operation under the next operating conditions and continued for 5 days. The ore is charged by dividing one charge (ch) into two batches, the small coke mixing amount per charge of ore is constant at 3.2 t / ch, and the small coke mixing amount in each batch of ore is The operation was carried out with various changes. Table 1 shows the test operation conditions and the operation results.

  In the table, the gas utilization rate is a value calculated by the following equation (2) based on the gas analysis value collected by the blast furnace rise pipe, and the larger the value, the higher the reduction efficiency.

Gas utilization rate = CO ₂ (%) × 100 / (CO (%) + CO ₂ (%)) (2)
Further, the blast furnace air flow resistance index (KR) is an index calculated by the following equation (3), and the smaller the value, the better the furnace air permeability.

KR = (P _B −P _T ) / L / (kμ ^β ρ ^1−β u ^2−β ) (3)
Where KR is the blast furnace ventilation resistance index (1 / m), P _B and P _T are the blowing pressure and the top pressure (Pa), L is the distance between the tuyere and the top (m), β and k are A constant determined by the form of the gas flow, μ is the gas viscosity (Pa · s), ρ is the gas density (kg / m ³ ), and u is the gas flow velocity (m / s) in the furnace.

  The test results were evaluated according to the methods shown in the margins of Table 1, classified into five stages A to E according to the furnace gas utilization rate and the blast furnace ventilation resistance index.

  Test numbers T1, T2 and T3 are tests of the present invention examples that satisfy the range specified in the present invention, and test numbers T4, T5 and T6 are tests of comparative examples outside the range specified in the present invention. .

  Test Nos. T2 and T3, which are examples of the present invention, have an FC2 / FC1 value of 1 or less, which is the ratio of the small coke mixing amount in the second ore batch and the small coke mixing amount in the first ore batch. As a result of the effect of promoting the reduction of ore and the reduction of ventilation resistance in the cohesive zone at the lower part of the furnace, the gas utilization rate is higher than that of the comparative example, and the blast furnace ventilation resistance index (KR) is also low. Thus, the air permeability in the furnace was good.

  Test No. T1, which is an example of the present invention, has a small coke deposition position of 0.3 or less, and the value of FC2 / FC1 is 0.3. Therefore, the gas utilization is higher than those of Test Nos. T2 and T3. The rate was high and the air permeability in the furnace was good.

  In contrast, the test number T4 of the comparative example in which the small coke was not mixed in the second ore batch, the test number T5 of the comparative example in which the ore was not mixed in the first ore batch, and the small coke The test numbers T6 of the comparative examples that were not deposited in the region within 30% of the furnace port radius from the furnace wall were the results of low gas utilization rate and poor in-furnace air permeability.

  According to the charging method of the bellless blast furnace according to the present invention, the ore is divided into two or more batches, and the mixing amount of the small coke into each batch and the charging position of the small coke into the furnace are determined. By optimizing, the effect of mixing the small coke can be maximized to improve the air permeability in the cohesive zone of the lower part of the furnace, and the stable operation of the blast furnace can be ensured by ensuring a stable gas flow in the furnace. it can.

  Further, even when the heat load on the furnace wall is high, an increase in the heat load on the furnace wall can be suppressed while improving the air permeability of the cohesive zone near the furnace wall.

As a result, the charging method of the present invention improves the air permeability in the lower zone cohesive zone, and the operation of the bell-less blast furnace as the charging method that contributes to the stabilization of the gas flow in the furnace. Widely applicable to.

Claims (2)

  A charge charging method for a bell-less blast furnace in which ore is divided and charged in two or more batches, and a small amount of coke having a particle size of 5 to 40 mm is mixed in each divided batch of ore to be charged. The amount of the small coke mixed in the first ore batch is made larger than the amount of the small coke mixed in the second ore batch or more, and the charge is charged from the furnace wall side toward the furnace center. To charge the bellless blast furnace. The position where the small coke mixed with ore is deposited in the furnace after entering the blast furnace and the furnace radial distance between the furnace wall and X is X, and the blast furnace radius is R, where the small coke is deposited. The method for charging a bell-less blast furnace according to claim 1, wherein the distance between the furnace and the furnace wall and the radius of the furnace port satisfy the relationship represented by the following formula (1).
X / R ≦ 0.3 (1)