JP2808344B2 - Blast furnace charging method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of charging a blast furnace raw material.

[Conventional technology]

In blast furnace operation, it is important to secure a high tapping rate by controlling the distribution of gas flow in the radial direction of the blast furnace and reducing the ventilation resistance inside the furnace while effectively using the reducing gas. Become. In the lower part of the blast furnace, there is a region called a cohesive zone, in which ore is softened and fused, and has a large airflow resistance, which controls the air permeability of the entire blast furnace and further controls the productivity.

In order to improve the permeability of the cohesive zone, it is known that a so-called mixed charging in which coke is mixed into the ore layer is effective,
Many techniques have been reported to obtain the proper mixing.

The following has been proposed as a charging method for creating an appropriate mixing state by mixing charging.

SUMMARY OF THE INVENTION These conventional techniques relate to a method of mixing different kinds of raw materials, particularly ore and coke, and charging the mixture into a furnace. This is a method in which ore and coke are charged into different furnace top hoppers, respectively, and the on-off valves of the charging device are simultaneously operated to deposit the ore and coke in a uniformly mixed state in the furnace.

[Problems to be solved by the invention]

In the bellless blast furnace, the amount of raw material charged into the furnace per unit time is small, so that the raw material undergoes segregation of particle size when flowing down the surface of the charged material in the furnace, and the raw material with large particle size is located ,
Raw material of small particle size is deposited on the periphery. Such natural segregation in the radial direction of particle size is inevitable in blast furnace operation. Also,
Utilizing such segregation, sharp blast furnace center gas flow,
By securing an appropriate furnace wall gas flow, an appropriate cohesive zone shape has been controlled.

When the mixed charging method is employed to reduce the airflow resistance of the cohesive zone, it is difficult to secure an appropriate blast furnace center gas flow in the above-described conventional technology for the following reasons.

Due to the mixed charging, the volume of the ore layer in which coke is mixed increases, the discharge speed of the raw material increases, segregation of the particle size in the furnace becomes insufficient, and the ore particle size in the center of the blast furnace decreases.

Due to the mixed charging, the volume of the ore layer in which the coke was mixed increased, and a larger amount of ore flowed into the center as compared with the conventional case, and the ore / coke ratio in the center increased.

These problems are all caused by an increase in the volume of the mixed layer (ore layer). However, it is difficult to reduce the amount of ore charged at one time for the following reasons.

(A) In a normally used two-hopper bellless blast furnace of the parallel hopper type, the number of times of charging controls the productivity, and it is not possible to cope with high productivity.

(B) If the thickness of the coke layer is too thin at the time of mixing and charging, the reproducibility of coke deposition in the radial direction becomes poor,
The control of the charge distribution is reduced. As a method for securing a blast furnace center gas flow, Japanese Patent Publication No. 64-9373 is known as a prior art. This technology is a coke charging method in which ore and coke are charged alternately into a blast furnace. The coke in each charge is divided into at least two lines over time, and most of the total coke charged in the charge Is charged so as to cover the entire ore layer, and the remaining coke is charged into the center of the furnace at the time of the final charging.

The following problems occurred when applied to the mixed charging method in which ore and coke were mixed in order to secure the blast furnace center gas flow and improve the permeability of the cohesive zone by the above method.

(B) When combined with the mixed charging method, even if the amount of coke charged into the center is constant, the center gas flow in the blast furnace may be excessive or the center gas flow in the blast furnace may be insufficient, resulting in poor reproducibility. poor. This is because the amount of coke charged in the center has an appropriate range according to the amount of coke mixed in the mixed charging.

(B) In the usual parallel two hopper type bellless charging apparatus, the number of times of charging is limited by the equipment, and it is difficult to apply the apparatus except during the production reduction operation.

The present invention seeks to solve the above-mentioned problems of the prior art in order to enable mixed charging to reduce the airflow resistance of the cohesive zone.

[Means for solving the problem]

The present invention employs the following technical means in a raw material charging method for alternately charging a mixture of ore and coke and coke in a blast furnace having a bellless charging device.

First, A% of the total charged coke amount is intensively charged into the furnace center.

Next, the remaining (100-A)% coke is charged over the entire blast furnace radius.

Thereafter, a mixture in which another coke is mixed in the ore by B% is charged.

 The above A and B satisfy the following relationship.

0.286B-0.286 <A <0.340B + 5.20 Next, the above order may be reversed, and in this case, A and B satisfy the following relationship.

0.286B-0.286 <A <0.340B + 4.0 The above methods are preferably performed using three or more furnace top hoppers in parallel.

[Action]

The present invention is a mixed charging method characterized in that charging is performed by the following method in order to solve the problems of the conventional mixed charging method.

That is, according to the present invention, first, coke is intensively charged into the central portion of the blast furnace, and then charged in the entire radial direction, and then the mixture is charged thereon.

By increasing the amount of coke charged into the center in accordance with the increase in the amount of coke mixed in, the amount of the mixed layer flowing into the center is controlled. As a result, a layer with a large amount of coke is stably formed in the central portion of the blast furnace, the central gas flow of the blast furnace can be secured, and the flow of the furnace wall can be appropriately controlled.

As a result, the furnace condition is stabilized, and it is possible to perform a high tapping ratio operation. When three or more hoppers are used in parallel, the present invention can be carried out smoothly.

FIG. 1 is a schematic partial cross-sectional view of a blast furnace showing a deposition behavior of a charge in the blast furnace 1 at the time of mixed charging. Fig. 1 (a)
In FIG. 1, a swing chute 2 is mounted on the upper part of the blast furnace 1. From the furnace top hopper, the central charging coke 5 is first charged into the center of the blast furnace, then the coke layer 3 is charged, and then the mixed layer (mixture layer of ore and coke) is charged.

If the amount of coke 5 charged in the center is too large, the ratio of the ore layer thickness to the coke layer thickness (L _O / L _C ) at the center decreases, and the central flow becomes excessive.

Also, even if the amount of coke 5 charged in the center is constant, if the amount of coke mixed in the mixed layer changes, the ore flowing into the center changes.

When the amount of mixed coke is increased, the amount of ore flowing into the center increases, so that it is necessary to increase the amount of coke charged into the center.

A similar tendency exists in the case of (b) in which the charging sequence is changed.

Therefore, in order to obtain a suitable central coke charging amount 5, an experiment was conducted by changing the central charging coke amount for various mixed charging amounts.

FIG. 3 is a graph showing the relationship between the blast furnace center gas flow and the central coke charge in the blast furnace.

The gas temperature at the center of the shaft gas sampler and the gas utilization rate at the center of the shaft gas sampler (CO
₂ / (CO ₂ + CO) varies greatly with the central coke charge. The preferred range of the gas temperature at the center of the shaft gas sampler is 600 to 800 ° C., and the preferred range of the gas utilization rate at the center of the shaft gas sampler is 25% or less. In order to set each of these values to a suitable range, there is a suitable central coke charging amount according to the mixed coke amount. When the mixed coke amount is as small as 1%, the central charging coke is not required, but it is necessary to increase the central coke charging amount as the mixed coke amount increases.

From FIG. 3, it can be seen that the preferred range of gas utilization in the central part of the shaft gas sampler is <25% and the preferred range of the central gas temperature is 60%.
The relationship between the mixed charging coke amount satisfying 0 to 800 ° C. and the central charging coke amount was determined and is shown in FIG.

FIG. 4 is a graph showing a preferable range of the amount of coke charged in the center according to the amount of mixed coke.

In FIG. 5, first, coke is charged over the entire blast furnace radius, and then the remaining coke is charged intensively in the center of the furnace.
Next, also in the case where a mixture in which another coke was mixed in B (%) into the ore was charged, a graph showing the preferred range of the amount of coke charged in the center according to the amount of mixed coke was obtained in the same procedure.

There is an optimum value for the amount of coke charged in the center depending on the amount of coke mixed. If the amount of coke charged in the center is too large, the center gas flow becomes excessive, while if it is too small, the center gas flow becomes insufficient. The limit value has a suitable range according to the mixed coke amount. The function representing the optimum value differs depending on the charging method, and the charging method of the raw material is such that first, the coke A (%) is intensively charged into the furnace center, and then the remaining (100-A)
(%) When the coke is charged over the entire blast furnace radius and then a mixture of B (%) mixed with another coke in the ore (in the case of FIG. 4), the lower limit is 0.286B-0.286. is there. The upper limit is indicated by 0.340B + 5.20.

The method of charging the raw materials is the first (100-A)
(%) Of coke is charged over the entire blast furnace radius, then the remaining entire coke of A (%) is intensively charged into the furnace center, and then another coke in the ore is B (%). When the mixed mixture is charged (in the case of FIG. 5), the lower limit is the same as above, but the upper limit is indicated by 0.340B + 4.0.

As described above, the purpose of the mixed charging method is to reduce the pressure loss in the cohesive zone, thereby improving the permeability of the blast furnace and increasing the tapping rate.

By combining the central charging method and the mixed charging method, air permeability in the furnace could be ensured.However, the number of batches per charge increased and The upper limit becomes rate-limiting.

FIG. 6 is an explanatory diagram showing the relationship between the number of hoppers provided in parallel and the number of times of charging.

The horizontal axis (a) 2 Batch 1 Charge (C-O charged cycle) (b) 3 Batch 1 Charge (C-C-O charged cycle) (c) 4 Batch 1 Charge (C-C-O _M Charging cycle). Where C is the coke charging, O ore charging, O _M denotes the mixture charging process.

The vertical axis indicates the number of times of charging per day. A preferred charging frequency is 150 times / day or more. In FIG. 6, the symbol △ indicates the capability of a vertical two-stage hopper, the symbol ○ indicates the capability of a two-parallel hopper, and the symbol ● indicates the capability of a three-parallel hopper.

In a normal two-parallel hopper, the number of charges cannot keep up in a cycle involving simultaneous discharge, and a complicated charge as in the present invention is difficult. When the tapping speed is low, mixed charging can be performed with a two-parallel hopper, but in a high tapping ratio operation, it is effective to use three or more parallel hoppers.

〔Example〕

FIG. 2 is a system diagram of a raw material charging path of the blast furnace. ore,
The raw material charged into the blast furnace discharged from the storage bin 11 for storing coke and the like is guided to the surge hopper 13 via the belt conveyor 12, and is fed to the blast furnace charging conveyor 14 to form the furnace top hopper 15 of the blast furnace 1.
Will be charged. The raw material cut out from the top hopper 15 is sprayed into the blast furnace 1 by the swirling chute 2 and charged so as to form an alternate layer of coke and ore. When mixing and charging coke into ore, the ore and coke are separately charged into the furnace top hopper 15 and discharged simultaneously, or the ore and coke separately stored in the surge hopper 13 are charged. , Or the ore and coke are simultaneously discharged from the storage bin 11 onto the belt conveyor 12. If there are three or more furnace top hoppers 15, the mixing charging operation becomes easy.

Next, Examples of the method of the present invention are shown in Table 1 in comparison with Comparative Examples (I) and (II).

 The charging method in Table 1 is as follows.

C ₁ -C ₂ -O _M: after loading of the center charging coke, total radius coke charged after mixing charging C ₂ -C ₁ -O _M: coke instrumentation after turning center charging coke total radius After charging, mix charging [Effects of the Invention] According to the present invention, a high tapping ratio operation can be achieved,
As a prerequisite, it was possible to secure a stable and sharp central flow, controllability of the furnace wall flow was good, and the central flow and peripheral flow could be controlled with good reproducibility.

In addition, the controllability of the charge distribution can be improved, the hot metal component can be stabilized, the fluctuation of the ventilation resistance decreases,
This has the effect of reducing raw material and fuel costs.

Further, the rate control on the equipment was eliminated by providing three or more hoppers in parallel at the furnace top, and the problem of charging coke alone at the center in mixed charging could be solved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a blast furnace, FIG. 2 is a system diagram of a raw material charging path of the blast furnace, FIG. 3 is a graph showing a relationship between a blast furnace center gas flow and a central coke charging amount in the blast furnace, and FIG. FIG. 5 is a graph showing the relationship between the amount of coke mixed and the amount of coke charged in the center, and FIG. 6 is a graph showing the relationship between the number of furnace top hoppers provided in parallel and the number of times of charging. 1 Blast furnace 2 Swirl chute 3 Coke layer 4 Mixed layer 5 Coke charged at the center 11 Storage bin 12 Belt conveyor 13 Surge hopper 14 Blast furnace Conveyor 15 ... Furnace top hopper

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshitaka Sawa 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Takuho Edo 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel (56) References JP-A-63-161104 (JP, A) JP-A-61-227109 (JP, A) JP-A-2-54706 (JP, A) Japanese Patent Publication No. 64-9373 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) C21B 5/00

Claims (3)

(57) [Claims] 1. A raw material charging method in which a mixture of ore and coke and coke are charged alternately in a blast furnace having a bellless charging device, first, A (%) of coke is intensively charged in the center of the furnace. And then the remaining (100-A) (%) coke is charged over the entire blast furnace radius and then another coke in the ore is B (%)
A method for charging a raw material for a blast furnace, wherein the mixed mixture is charged and A and B satisfy the following relationship. 0.286B-0.286 <A <0.340B + 5.20 2. A raw material charging method in which a mixture of ore and coke and a coke are charged alternately in a blast furnace having a bellless charging device, wherein (100-A) (%) of the coke is first converted into a blast furnace radius. Charging the whole, then intensively charging the remaining total A (%) coke into the furnace center, then charging a mixture of B (%) with another coke in the ore, and A,
A method for charging a blast furnace raw material, wherein B satisfies the following relationship. 0.286B-0.286 <A <0.340B + 4.0 3. A method for charging a blast furnace raw material according to claim 1, wherein the raw material is charged into the blast furnace using three or more furnace top hoppers in parallel.