CN109072318B - Method for charging raw material into blast furnace - Google Patents

Method for charging raw material into blast furnace Download PDF

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CN109072318B
CN109072318B CN201780017142.0A CN201780017142A CN109072318B CN 109072318 B CN109072318 B CN 109072318B CN 201780017142 A CN201780017142 A CN 201780017142A CN 109072318 B CN109072318 B CN 109072318B
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coke
layer
mixed
blast furnace
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CN109072318A (en
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市川和平
柏原佑介
大山伸幸
津田和吕
山平尚史
石井邦彦
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JFE Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B5/00—Making pig-iron in the blast furnace
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B5/00—Making pig-iron in the blast furnace
    • C21B5/008—Composition or distribution of the charge
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B7/00—Blast furnaces
    • C21B7/18—Bell-and-hopper arrangements
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B7/00—Blast furnaces
    • C21B7/24—Test rods or other checking devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices

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  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacture Of Iron (AREA)
  • Blast Furnaces (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)

Abstract

In a blast furnace operation performed by forming a coke mixed ore layer and a coke layer in a blast furnace, the amount of coke mixed in the coke mixed ore layer is appropriately controlled in accordance with the content of powdery coke in the coke forming the coke layer, thereby ensuring the gas permeability inside the blast furnace. A method for charging a raw material into a blast furnace, wherein a coke-mixed ore layer and a coke layer are formed in a layered manner, wherein the ratio of coke particles having a short diameter of 5mm to 35mm or less in the coke is measured by a particle size measuring sensor provided above a conveying means for conveying the coke forming the coke layer, and when a condition that the coke for forming the coke layer does not contain the coke particles having a short diameter of 35mm or less is defined as a reference condition, the amount of coke mixed in the mixed raw material is set to be smaller than the amount of coke mixed under the reference condition based on the measured ratio, and the amount of coke different from the reference condition is blended as the coke forming the coke layer.

Description

Method for charging raw material into blast furnace
Technical Field
The present invention relates to a method for charging a blast furnace with raw materials. More specifically, the present invention relates to a method for charging a blast furnace with raw materials, comprising: in a blast furnace operation in which a coke mixed ore layer and a coke layer are formed into a layered structure in a blast furnace, the amount of coke mixed in the coke mixed ore layer is appropriately controlled in accordance with the properties of the coke forming the coke layer, thereby ensuring the air permeability in the blast furnace.
Background
In recent years, reduction of CO has been demanded from the viewpoint of prevention of global warming2. In the iron and steel industry, CO2About 70 mass% of the discharge amount is discharged from a blast furnace for pig iron production, and therefore, it is required to reduce CO from the blast furnace2And (4) discharging the amount. The reduction of CO in the blast furnace can be achieved by reducing the reducing material (coke, coal powder, natural gas, etc.) used in the blast furnace2. In a blast furnace, iron ore (also referred to simply as "ore") as a raw material and coke as a reducing material are charged from a furnace top so as to be layered alternately, and a mineral layer and a coke layer are formed in the blast furnace.
On the other hand, when reducing the reducing material, particularly coke, the amount of coke that ensures the air permeability in the blast furnace decreases, and the air permeability resistance in the blast furnace increases. In a general blast furnace, if iron ore charged from the top of the furnace reaches a temperature at which it starts to soften, voids are filled in the ore layer by the dead weight of the raw material existing in the upper portion, and the ore layer is deformed. Therefore, in the lower part of the blast furnace, the gas permeation resistance of the ore layer is very high, and a molten layer (referred to as "reflow zone") in which gas hardly flows is formed. The air permeability of the reflow belt greatly affects the air permeability of the whole blast furnace, and limits the productivity of the blast furnace.
As a method for improving the gas permeability resistance of the reflow zone, it is known that it is effective to charge a raw material (referred to as "mixed raw material") in which an ore and coke having a relatively small particle size are mixed and coke having a relatively large particle size are alternately charged into a blast furnace, and form a coke mixed ore layer composed of the mixed raw material and a coke layer composed of the coke having a relatively large particle size in a layered manner. That is, it is known that it is effective to mix coke in the ore layer, and many techniques for forming a coke-mixed ore layer have been proposed.
For example, patent document 1 proposes 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 the ore by a conveyor, 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 proposes the following technique: in a bell-less blast furnace, when coke or ore stored in a plurality of top bunkers is charged from a furnace center portion toward a furnace wall portion in a radial direction of the furnace, the ore stored in one of the top bunkers starts to be discharged from the other top bunkers and the coke and ore are charged at the same time from a time point when a discharge amount of the coke stored in the other top bunkers reaches a predetermined amount between 5 and 50 mass% of a coke charge amount of 1 batch. Thus, 3 batches, i.e., a normal coke charging batch, a center coke charging batch, and a mixed coke charging batch, can be performed simultaneously.
Patent document 3 proposes a technique for charging the following raw materials: in order to prevent the instability of the shape of the reflow zone and the reduction 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 ore and all the coke are completely mixed and charged into the blast furnace.
In addition, patent document 4 proposes the following technique as a method for utilizing the reactivity improvement effect of the coke after mixing: 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.
On the other hand, since the amount of coke charged into the furnace (also referred to as "coke ratio") is almost constant, the thickness of the coke layer is relatively reduced when coke is mixed into the ore. It is empirically known that if the thickness of the coke layer is reduced in the blast furnace, the gas permeation resistance of the soft melting zone in which the ore is softened and melted increases, and stable operation is hindered.
In order to prevent such an increase in the air permeation resistance due to the decrease in the thickness of the coke layer, some proposals have been made. For example, patent document 5 proposes the following technique for preventing a local reduction in the focal layer thickness: the charging range of the coke at the furnace mouth is set to a region of 40% or more from the furnace wall side in the furnace radial direction, and the average layer thickness of 1 layer of the coke at the furnace mouth is set to 60cm or more. Further, patent document 6 proposes the following technique: the coke charging amount at the furnace top is adjusted so that the coke layer thickness at the furnace belly becomes 250mm or more on average.
Patent documents 5 and 6 are operating conditions in the case where a large amount of coke is not mixed in the ore, and when a large amount of coke is mixed in the ore, the permeability of the coke-mixed ore layer (ore layer) is improved, and therefore the lower limit value of the coke layer thickness should be able to be relaxed.
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. Sho 64-36710
Patent document 5: japanese laid-open patent publication No. 7-18310
Patent document 6: japanese laid-open patent publication No. 11-506393
Disclosure of Invention
However, although the coke used for forming the coke layer is screened by a screen having a predetermined mesh size, the coke having a size not larger than the mesh size of the screen (hereinafter, also referred to as "powdery coke") cannot be screened completely. Therefore, in a normal blast furnace operation, the properties of the coke forming the coke layer vary, and the content of powdery coke in the coke layer varies according to the properties of the coke.
In the coke layer, if the content of the powdery coke increases, the permeability deteriorates, and therefore, in such a case, it is necessary to increase the thickness of the coke layer to ensure the permeability of the coke layer, that is, the permeability of the blast furnace. Increasing the thickness of the coke layer requires a decrease in the amount of coke mixed in the raw material mixture. This is because mixing is not reduced if not reducedThe amount of coke mixed in the raw material is excessive, not only CO2The amount of emissions increases and the manufacturing cost also increases.
That is, in order to perform a stable blast furnace operation, it is necessary to detect the content of powdery coke in the coke forming the coke layer in advance, and to increase or decrease the thickness of the coke layer and simultaneously decrease or increase the amount of coke mixed in the mixed raw material according to the detected content of powdery coke. However, the above patent documents 1 to 6 do not consider any of these points.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for charging a blast furnace with a raw material, in which a coke-mixed ore layer and a coke layer are formed in a layered manner in the blast furnace, wherein the thickness of the coke layer is increased or decreased depending on the content of powdery coke in the coke forming the coke layer, and the amount of coke mixed in the coke-mixed ore layer is appropriately controlled, thereby ensuring the gas permeability in the blast furnace.
The gist of the present invention for solving the above problems is as follows.
[1] A method for charging a blast furnace with a raw material mixture comprising iron ore and coke, wherein the raw material mixture and the coke are alternately charged from the top of the blast furnace,
a coke-mixed ore layer comprising the above-mentioned raw materials and a coke layer comprising the above-mentioned coke are formed in layers in the furnace,
wherein the ratio of coke particles having a particle diameter of 5mm to 35mm or less is measured by a particle diameter measuring sensor disposed above a conveying means for conveying the coke forming the coke layer to the blast furnace,
when the condition that the coke used for forming the coke layer does not contain coke particles having a short diameter of 35mm or less is defined as a reference condition, the amount of coke mixed in the raw material mixture is set to be smaller than the amount of coke mixed in the raw material mixture under the reference condition based on the ratio measured,
the coke in the difference between the coke blending amount under the reference condition and the coke blending amount set based on the above ratio is distributed as the coke forming the coke layer.
[2] The method of charging a raw material into a blast furnace according to the above [1], wherein the amount of coke mixed in the raw material mixture is set to be not more than an upper limit of the amount of coke mixed calculated by substituting the measured ratio into the following expression (1).
MIX＝[(9/10)×α－69/2]×β+200···(1)
(1) Where MIX is an upper limit value of the amount of coke mixed in the raw material mixture (kg/ton of molten iron), α is a short diameter of the coke particles and is an arbitrary value in a range of 5mm to 35mm, and β is a ratio (% by mass) of the coke particles having a short diameter of α mm or less.
In the method of charging a raw material into a blast furnace for forming a layer of a coke-mixed ore layer and a coke layer, the particle size distribution of coke for forming the coke layer is measured in a device for feeding the coke to the blast furnace. Then, based on the measurement result of the particle size distribution, the amount of coke to be mixed into the coke-mixed ore layer is set, and the amount of coke is distributed as the coke forming the coke layer, based on the difference between the set amount of coke to be mixed and the amount of coke to be mixed under the reference condition, that is, the amount of coke to be mixed when the ratio of the coke particles having a short diameter of 35mm or less to the coke forming the coke layer is zero. As a result, in the case of coke having a large coke content of fine particles, the thickness of the coke layer increases, and as a result, the air permeability of the coke layer, that is, the air permeability in the blast furnace is ensured, thereby stabilizing the operation of the blast furnace.
Drawings
FIG. 1 is a diagram defining the minor diameter of coke particles.
FIG. 2 is a schematic view of a test apparatus for measuring the relationship between the thickness of the coke layer and the air permeation resistance of the reflow zone.
FIG. 3 is a graph showing the relationship between the ratio of coke particles having a short diameter of 5mm or less and the upper limit value of the amount of coke to be mixed in the raw material mixture.
FIG. 4 is a graph showing the relationship between the ratio of coke particles having a short diameter of 35mm or less and the upper limit value of the amount of coke to be mixed in the raw material mixture.
FIG. 5 is a graph showing the relationship between the ratio beta when the upper limit value MIX is 50 kg/ton of molten iron and the minor axis alpha of coke particles.
Detailed Description
The present invention will be described in detail below.
In a blast furnace operation in which a coke-mixed ore layer composed of a mixed raw material of iron ore and coke and a coke layer are formed in a layered manner in a blast furnace, if the content of powdery coke (coke having a size not larger than the mesh size of a screen) in the coke for forming the coke layer increases, the gas permeability of the coke layer, that is, the gas permeability inside the blast furnace deteriorates. Therefore, in this case, it is necessary to reduce the amount of coke mixed into the coke-mixed ore layer, charge a portion corresponding to the reduced amount as a coke layer, and increase the thickness of the coke layer to ensure the air permeability inside the blast furnace.
The present inventors have conducted tests using a test apparatus capable of simulating the air permeability resistance of the reflow zone in the blast furnace for the purpose of stably ensuring the air permeability in the blast furnace even when the content of the powdery coke used for forming the coke layer changes.
Generally, the coke forming the coke layer is screened by a screen having a mesh size of 35mm, transferred to a blast furnace, and charged into the blast furnace. It is common knowledge to those skilled in the art that if coke is of a size that cannot pass through a sieve having a mesh size of 35mm, the permeability of the reflow zone inside the blast furnace can be ensured. However, coke particles having a size to be removed by the sieve having a mesh size of 35mm are also mixed in the coke after the sieving by the sieve having a mesh size of 35 mm. In addition, the coke is pulverized by a drop impact or the like during the conveyance to the blast furnace.
In the present specification, the coke having a size to be removed by a sieve having a mesh size of 35mm, which is contained in the coke forming the coke layer, is referred to as "coke having a short diameter of 35mm or less". Similarly, coke having a size to be screened by a sieve having a mesh size of α mm is referred to as "coke having a short diameter of α mm or less". Here, as shown in fig. 1, "short diameter of coke particles" is defined as the distance between intersection points when the distance between the intersection points of the straight line passing through the center of gravity of the coke particles and the outer periphery of the projection plane is shortest on the projection plane of the coke particles.
In the test, focusing on the content of coke particles having a short diameter of 35mm or less in the coke forming the coke layer, the relationship between the content ratio of any coke particles having a short diameter of 5mm to 35mm and the amount of coke mixed in the coke mixed ore layer was examined as a condition for ensuring the permeability of the reflow zone in the blast furnace.
Fig. 2 is a schematic diagram of a test apparatus for measuring the relationship between the thickness of the coke layer and the air permeation resistance of the reflow zone. In the figure, reference numeral 1 denotes a sample heating furnace, and the sample heating furnace 1 includes a sample-filled container 2 and a heating device 3 inside thereof. Further, a sample-filled layer 6 in which the coke layer 4 and the coke-mixed rock layer 5 are filled in a layered state is formed inside the sample-filled container 2. The temperature of the sample packed layer 6 is controlled by the heating device 3. Reference numeral 7 denotes a gas heating furnace, and the gas heating furnace 7 also includes a heating device 8 therein. Reference numeral 9 denotes a gas mixer, 10 denotes a pipe for gas flow, 11 denotes a pressure gauge, 12 denotes a thermocouple, 13 denotes a pressure plate, 14 denotes a base, and 15 denotes a connecting rod, and the connecting rod 15 is preferably made of graphite or metal. Note that reference numeral 16 denotes a load mechanism, and in this example of the test apparatus, a weight 16 is used as the load mechanism. Then, the weight 16 applies a load to the sample packed layer 6 in the simulated blast furnace.
As shown in the drawing, the largest feature of this test apparatus is that the sample heating furnace 1 and the gas heating furnace 7 are arranged in series, and by this series arrangement, the gas heated by the gas heating furnace 7 enters the sample heating furnace 1 from the lateral direction.
In this test apparatus, the coke layer 4 was formed by using coke in which the ratio of particles having a short diameter of 5mm or less was adjusted to a range of 0 to 5.0 mass% and coke in which the ratio of particles having a short diameter of 35mm or less was adjusted to a range of 0 to 50 mass%, and the amount of coke mixed in the coke-mixed mineral layer 5 was variously changed to examine the air permeability. In the present specification, the condition that the coke used for forming the coke layer does not contain coke particles having a short diameter of 35mm or less is defined as a reference condition.
Specifically, the amount of coke mixed in the coke-mixed ore layer 5 under the standard condition, in which the ratio of the coke particles having a short diameter of 35mm or less to the coke for forming the coke layer is zero, is set to 200 kg/ton of molten iron. In addition, since the gas permeability is deteriorated as the content of the powdery coke in the coke for forming the coke layer 4 is increased, the coke mixed in the coke-mixed ore layer 5 is distributed to the coke layer 4 under various conditions to ensure the gas permeability, and the gas permeability is examined. Then, the coke mixing ratio (kg/ton of molten iron) in the coke-mixed ore layer 5 in the test in which the pressure loss in the test was equal to the pressure loss in the standard condition (condition not including coke particles having a short diameter of 35mm or less) was determined from the ratio of particles having a short diameter of 5mm or less and the ratio of particles having a short diameter of 35mm or less.
The results obtained in the test are shown in fig. 3 and 4. FIG. 3 is a graph showing the relationship between the ratio of coke particles having a short diameter of 5mm or less and the upper limit value of the amount of coke mixed in the raw material mixture in a test using coke in which the ratio of particles having a short diameter of 5mm or less is changed. FIG. 4 is a graph showing the relationship between the ratio of coke particles having a short diameter of 35mm or less and the upper limit value of the amount of coke mixed in the raw material mixture in a test using coke in which the ratio of particles having a short diameter of 35mm or less is changed. In fig. 3 and 4, the coke mixing ratio (kg/ton of molten iron) at which the pressure loss equivalent to that of the reference condition is achieved is shown as an upper limit value.
As shown in FIGS. 3 and 4, the ratio of particles having a short diameter of 5mm or less or 35mm or less on the horizontal axis and the upper limit of the amount of coke mixed in the raw material mixture on the vertical axis are linearly related to each other. From this relationship, it can be seen that: the ratio of the upper limit of the amount of coke mixed in the raw material mixture to the coke particles having a minor axis of 5mm or less or 35mm or less is expressed by a linear equation. Further, the influence of the ratio of coke particles on the upper limit value of the coke mixing amount differs between the case where the short diameter is 5mm or less and the case where the short diameter is 35mm or less.
Thus, if the upper limit of the amount of coke mixed in the raw materials is MIX (kg/ton of molten iron), the short diameter of the coke particles is α (mm), and the ratio of the coke particles having a short diameter of 5mm or less or 35mm or less is β (mass%), these factors are expressed by the following expression (2). The coke content (kg/ton of molten iron) in formula (2) with reference numeral 200 is a coefficient A, B.
MIX＝(A×α+B)×β+200···(2)
If the coefficient a and the coefficient B are obtained by substituting the conditions in fig. 2 for the condition that MIX is 50 kg/ton of molten iron when the ratio β of the coke particles having a short diameter of 5mm or less in fig. 3 is 5 mass% and the condition that MIX is 50 kg/ton of molten iron when the ratio β of the coke particles having a short diameter of 35mm or less in fig. 4 is 50 mass%, a is 9/10 and B is-69/2. That is, the formula (2) is represented by the following formula (1).
MIX＝[(9/10)×α－69/2]×β+200···(1)
In the formula (1), MIX is an upper limit value (kg/ton molten iron) of the amount of coke mixed in the raw material mixture, α is a short diameter of the coke particles and is an arbitrary value in a range of 5mm to 35mm, and β is a ratio (mass%) of the coke particles having a short diameter of α mm or less.
In order to confirm the validity of the expression (1), the ratio of coke particles having a short diameter of 20mm or less was changed, and the ratio β of coke particles having a short diameter of 20mm or less was determined when the upper limit value MIX of the coke content reached 50 kg/ton of molten iron. As a result, it was found that the upper limit MIX of the amount of coke mixed was 50 kg/ton of molten iron when the ratio beta of the coke particles having a short diameter of 20mm or less was 28 mass%.
In the tests in which α is 5mm, α is 20mm, and α is 35mm, the ratios β of the upper limit MIX to 50 kg/ton of molten iron were compared. Fig. 5 is a graph showing the relationship between the ratio β and the short diameter α, with the horizontal axis representing the short diameter α (mm) of coke particles and the vertical axis representing the ratio β (mass%) when the upper limit value MIX reaches 50 kg/ton of molten iron. From FIG. 5, it is understood that the ratio β (% by mass) of the upper limit value MIX to 50 kg/ton of molten iron and the short diameter α (mm) of the coke particles are in a linear equation. That is, it can be confirmed that the formula (1) is appropriate when α is in the range of 5 to 35 mm.
Although the formula (1) is a case where the amount of coke mixed in the coke-mixed ore layer in which the ratio of coke particles having a short diameter of 35mm or less in the coke for forming the coke layer is zero (reference condition) is 200 kg/ton of molten iron, the amount of coke mixed in the reference condition is not necessarily limited to 200 kg/ton of molten iron when the present invention is carried out.
In the blast furnace operation, the coke ratio (kg/ton molten iron) required for the reduction reaction of the iron ore and the temperature rise of the molten iron produced is generally about 300 kg/ton molten iron, but varies depending on the operating conditions of each blast furnace. The coke ratio is the total coke charge (kg/ton of molten iron) added to both the coke-mixed ore layer and the coke layer. That is, if the coke ratio is CR (kg/ton molten iron), the amount of coke to be incorporated into the coke-mixed ore layer under the standard conditions can be represented by the amount (CR × γ) obtained by multiplying the coke ratio CR by a certain incorporation ratio γ (-).
The present invention has been made based on the above test results, and a method for charging a raw material into a blast furnace according to the present invention is a method for alternately charging a raw material mixture in which iron ore and coke are mixed and coke from a blast furnace top, and forming a coke mixed ore layer composed of the raw material mixture and a coke layer composed of the coke in a layer-like manner in the furnace, wherein a ratio of coke having an arbitrary short diameter or less in a range of 5mm to 35mm in the short diameter of particles contained in the coke transported by a transportation means (a conveyor belt or the like) for transporting the coke for forming the coke layer to the blast furnace is measured by the particle size measuring sensor provided above the transportation means, and based on the measured ratio, the amount of coke mixed in the raw material is set to be less than a coke mixed amount in which a ratio of coke particles having a short diameter of 35mm or less in the coke for forming the coke layer is zero under a reference condition, the coke in the difference between the coke blending amount under the reference condition and the coke blending amount set based on the above ratio is distributed as the coke forming the coke layer. That is, in the blast furnace operation in which the coke ratio (kg/ton molten iron) is constant, the coke amount, which is a difference between the coke blending amount under the reference condition and the coke blending amount set based on the content of powdery coke in the coke for forming the coke layer 4, is allocated as the coke for forming the coke layer.
It should be noted that the difference in the coke amount is preferably adjusted from the coke mixing layer to the coke layer because the air permeability can be ensured without increasing or decreasing the reducing agent ratio, and the adjustment amount can be allowed to ± 5 kg/ton of molten iron.
When the coke to be blended in the coke mixing layer is blended in the coke layer, it is preferable that the blending amount of the coke in the raw material mixture is set to be not more than the upper limit of the blending amount of the coke calculated by substituting the measured ratio into the above expression (1).
That is, if the fine particles (having a short diameter of 35mm or less) contained in the coke forming the coke layer increase, the permeability of the coke layer deteriorates, and therefore, in order to ensure the permeability, in the present invention, the coke originally blended in the coke mixed ore layer is distributed to the coke layer, thereby ensuring the permeability inside the blast furnace. By adjusting the coke amount in this manner, the coke ratio (kg/ton of molten iron) is maintained at a predetermined value.
As a particle size measuring sensor for measuring the particle size distribution of coke, for example, a measuring apparatus based on the particle size distribution measuring method disclosed in publication 1 (publication 1; Japanese patent application laid-open No. 2003-83868) and the like can be used. Publication 1 discloses "a particle size distribution measurement method in which an image of an object to be measured is captured by an imaging device, a blurred image obtained by blurring an original image is obtained from the captured original image, the blurred image is binarized to measure the distribution of particle sizes of the object to be measured having a predetermined particle size or larger, a difference image formed by a difference between the captured original image and the blurred image is binarized to measure the distribution of particle sizes of the object to be measured having a particle size smaller than the predetermined particle size, and the entire particle size distribution is measured based on the measurement results of the 2 particle size measurement distributions". Specifically, a particle size measuring sensor capable of detecting the distance between the intersections shown in fig. 1 by image processing is used.
As described above, according to the present invention, the particle size distribution of the coke forming the coke layer is measured in the facility for transporting the coke to the blast furnace, and the amount of the coke mixed into the coke-mixed ore layer and the amount of the coke mixed into the coke layer are controlled based on the measurement result of the particle size distribution, thereby ensuring the air permeability in the blast furnace and stabilizing the operation of the blast furnace.
Examples
In the case where the raw material charging was carried out by applying the present invention under the conditions of the same coke ratio and the same tapping ratio in the actual blast furnace and the case where the raw material charging was carried out outside the range of the present invention, the gas utilization rate and the pressure loss of the packed bed were examined, and the results of the examination were described in comparison. As a particle size measuring sensor for measuring the particle size distribution of coke, a measuring device based on the particle size distribution measuring method disclosed in publication 1 was used, and the measuring device was disposed above a conveyor belt for conveying coke for forming a coke layer to a blast furnace.
In the coke used for forming the coke layer, the ratio of coke particles having a short diameter of 5mm or less is measured by a particle size measuring sensor. The results are shown in table 1, in which the case where the amount of coke mixed in the mixed raw material (kg/ton of molten iron) is adjusted to be not more than the upper limit value MIX (kg/ton of molten iron) of the amount of coke mixed calculated by substituting the measured value of the ratio of coke particles having a short diameter of not more than 5mm into expression (1) (inventive examples 1 and 2), and the case where the amount of coke mixed in the mixed raw material (kg/ton of molten iron) exceeds the upper limit value of expression (1) (comparative examples 1 and 2) are compared.
[ Table 1]
Figure GDA0001798613160000101
In addition, in the coke for forming the coke layer, the ratio of coke particles having a short diameter of 35mm or less was measured by a particle size measuring sensor. The results of comparison between the cases (inventive examples 3 and 4) in which the amount of coke mixed in the raw material mixture (kg/ton of molten iron) was adjusted to be equal to or less than the upper limit MIX (kg/ton of molten iron) of the amount of coke mixed calculated by substituting the measured value of the ratio of coke particles having a short diameter of 35mm or less into expression (1) and the cases (comparative examples 3 and 4) in which the amount of coke mixed in the raw material mixture (kg/ton of molten iron) exceeded the upper limit of expression (1) are shown in table 2.
[ Table 2]
Figure GDA0001798613160000111
From tables 1 and 2, it was confirmed that the gas utilization rate was improved and the pressure loss of the packed layer was reduced in the case of applying the present invention. That is, it was confirmed that a stable blast furnace operation can be achieved by applying the present invention.
Description of the symbols
1 sample heating furnace
2 sample filling container
3 heating device
4 coke layer
5 layer of coke mixed ore
6 sample Filler layer
7 gas heating furnace
8 heating device
9 gas mixer
10 piping for gas circulation
11 pressure gauge
12 thermocouple
13 pressing plate
14 base
15 connecting rod
16 hammer

Claims (2)

1. A method for charging a blast furnace with a raw material,
alternately charging a mixed raw material mixed with iron ore and coke and the coke from the top of a blast furnace,
a coke-mixed ore layer made of the mixed raw material and a coke layer made of the coke are formed in layers in the furnace,
wherein the ratio of coke particles having a particle diameter of 5mm to 35mm or less is measured by a particle diameter measuring sensor disposed above a conveying means for conveying the coke forming the coke layer to the blast furnace,
when the condition that the coke used for forming the coke layer does not contain coke particles with a short diameter of 35mm or less is defined as a reference condition, a coke blending amount which achieves a pressure loss equal to that of the reference condition is calculated based on the short diameter of the coke particles and the ratio measured, and the coke blending amount in the raw material mixture is set to be equal to or less than the calculated coke blending amount,
and allocating coke of a difference between the coke mixing amount under the reference condition and the set coke mixing amount as coke forming a coke layer.
2. The method of charging a blast furnace with a raw material according to claim 1, wherein the amount of coke mixed in the raw material mixture is set to be equal to or less than an upper limit value of the amount of coke mixed calculated by substituting the measured ratio into the following expression (1),
MIX＝[(9/10)×α－69/2]×β+200···(1)
in the formula (1), the compound (I),
MIX is the upper limit value of the coke mixing amount in kg/ton molten iron in the mixed raw materials,
alpha is the short diameter of coke particles and is 5mm,
beta is a ratio of coke particles having a minor axis of 5mm or less in mass%.
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