JP6885282B2 - Blast furnace operation method - Google Patents

Description

The present invention relates to a blast furnace operating method in which pulverized coal having improved transportability is blown from the tuyere of a blast furnace and pulverized coal used in the blast furnace operating method.

In recent years, global warming due to an increase in carbon dioxide emissions has become a problem, and _{controlling CO 2} emissions is also an important issue in the steel industry. In response to this, in recent blast furnace operations, the ratio of low reducing agent (low RAR: Reduction Agent Rate) is the total of the reducing agent blown from the tuyere and the coke charged from the top of the pig iron per 1 ton of pig iron. Quantity) Operations are being strongly promoted. The blast furnace mainly uses coke and pulverized coal blown from the tuyere as reducing agents, and in order to achieve a low reducing agent ratio and suppression of carbon dioxide emissions, a large amount of pulverized coal is used under conditions where there are as few operational troubles as possible. It is effective to inject carbon dioxide to reduce the coke ratio.

The pulverized coal is air-flowed using a pipe and finally blown into the blast furnace through the tuyere, but the pipe may be blocked due to the adhesion of the pulverized coal into the pipe. One of the factors that cause pulverized coal to adhere to the pipe is the particle size distribution of pulverized coal.

In Patent Document 1, the change over time in the particle size distribution of pulverized coal is measured, and the particle size distribution of pulverized coal is measured based on the mass ratio of the particle size of -44 μm and the mass ratio of the particle size of -74 μm in the pulverized coal. However, a method for blowing pulverized coal is disclosed, in which the pulverized coal is blown so that the particle size distribution of the pulverized coal is "45 mass% ≤ -44 μm ≤ 50 mass%, 60 mass% ≤ -74 μm".

Further, in Patent Document 2, attention is paid to the interparticle adhesive force of pulverized coal as an index other than the particle size, and the value of the interparticle adhesive force calculated based on the Rumpf equation is 3.26 × ^10-7 N or less. A method of blowing pulverized coal into a blast furnace is disclosed.

Japanese Unexamined Patent Publication No. 2013-43998 Japanese Unexamined Patent Publication No. 2016-1136664

In the technique disclosed in Patent Document 1, regardless of the coal brand, an attempt is made to prevent blockage of the pipe by adjusting the particle size distribution so that "45 mass% ≤ -44 μm ≤ 50 mass%, 60 mass% ≤ -74 μm". .. However, depending on the coal brand, there is a problem that the number of closed pipes increases even if the particle size distribution is adjusted.

Further, in the technique disclosed in Patent Document 2, the coal brand is selected based on the value of the interparticle adhesion force based on the Rumpf formula, but the pulverized coal adheres to the pipe as a powder layer when the pipe is closed, so that the pulverized coal adheres to the pipe. When the particle size of the coal changes or the porosity of the pulverized coal powder layer changes, there is a problem that the tensile breaking strength of the pulverized coal powder layer changes and the pipe is blocked.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to increase the coke ratio by blowing pulverized coal, which can suppress the blockage of pipes by pulverized coal, from the blast furnace tuyere. The purpose is to provide a method of operating a blast furnace that can be suppressed.

The features of the present invention that solve such a problem are as follows.
(1) A blast furnace operating method in which blast furnace tuyere is blown into the blast furnace. The blast furnace is charged into a cell composed of an upper cell and a lower cell, and is compressed with a compressive stress of 4.0 MPa for 60 seconds. The produced pulverized coal powder layer is pulled upward at a speed of 0.1 mm / sec between the upper cell and the pulverized coal powder layer while the lower cell is fixed, and the tensile breaking strength required to divide the blast furnace powder layer is A blast furnace operating method of 50 kPa or less.
(2) A blast furnace operating method in which blast furnace tuyere is blown into the blast furnace. The blast furnace is charged into a cell composed of an upper cell and a lower cell, and is compressed with a compressive stress of 4.0 MPa for 60 seconds. A method for operating a blast furnace, wherein the produced pulverized coal powder layer has a porosity of 0.35 or more.
(3) The blast furnace operating method according to (1) or (2), wherein the pulverized coal is heat-treated pulverized coal.
(4) The blast furnace operating method according to (3), wherein the pulverized coal is pulverized coal that has been heat-treated at 300 ° C. or higher.
(5) A pulverized coal powder layer prepared by being charged into a cell composed of an upper cell and a lower cell and compressed at a compressive stress of 4.0 MPa for 60 seconds with the upper cell while the lower cell is fixed. A pulverized coal having a tensile breaking strength of 50 kPa or less required for pulling the pulverized coal powder layer upward at a speed of 0.1 mm / sec and dividing the powder layer.
(5) The pulverized coal powder layer, which is charged into a cell composed of an upper cell and a lower cell and compressed for 60 seconds with a compressive stress of 4.0 MPa, has a porosity of 0.35 or more. ..

By implementing the blast furnace operation method of the present invention, it is possible to carry out blast furnace operation while suppressing blockage of pipes due to pulverized coal. As a result, deterioration of air permeability in the blast furnace and decrease in temperature can be suppressed, and an increase in coke ratio can be suppressed.

It is a schematic diagram which shows the blast furnace which can carry out the blast furnace operation method which concerns on this embodiment, and the peripheral part thereof. It is a schematic diagram explaining the measuring method of the tensile breaking strength. It is a graph which shows the relationship between the heat treatment temperature of the pulverized coal B and the pulverized coal X having different properties from the pulverized coal B, and the tensile breaking strength of the pulverized coal powder layer. It is a graph which shows the relationship between the heat treatment temperature of the pulverized coal B and the pulverized coal X having different properties from the pulverized coal B, and the porosity of the pulverized coal powder layer. It is a graph which shows the relationship between the volatile content of pulverized coal, and the circularity. It is a graph which shows the relationship between the circularity of a pulverized coal, and the porosity of a pulverized coal pulverized coal layer.

Hereinafter, the blast furnace operation method according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a blast furnace and its peripheral portion where the blast furnace operation method according to the present embodiment can be implemented. A method of blowing pulverized coal from the blast furnace tuyere will be described with reference to FIG. The coal 10 stocked in the yard is stored in the coal hopper 12. The coal 10 stored in the coal hopper 12 is cut out by the feeder 14 into the pulverized coal production apparatus 16. In the pulverized coal production apparatus 16, the coal 10 is crushed and dried to prepare pulverized coal 18 having a predetermined particle size.

The pulverized coal 18 thus prepared is airflow-conveyed to the bag filter 22 via the main pipe 20. Next, the pulverized coal 18 collected in the bug filter 22 is stored in the cole bin 24, and then stored in the blowing tank 26. The pulverized coal 18 housed in the blowing tank 26 is air-flowed to the distributor 28 and distributed from the distributor 28 to a large number of tuyere 38s at the bottom of the blast furnace 34 through a plurality of branch pipes 30 and a blow pipe 32. To. The pulverized coal 18 is injected from the lance 36 into the hot air supplied from the hot air furnace 40 to the blow pipe 32, and is blown into the blast furnace 34 from the tuyere 38 together with the hot air to burn. In this way, the pulverized coal 18 is blown from the tuyere 38 of the blast furnace 34 to operate the blast furnace 34.

The pulverized coal 18 is blown from the tuyere 38 of the blast furnace 34 through some piping systems, valves, blowing devices and the like. However, when a large amount of pulverized coal 18 is blown into the blast furnace 34, the pulverized coal 18 may adhere to the inner wall of the pipe, and the powder layer of the adhered pulverized coal 18 may grow and block the pipe.

On the other hand, in the blast furnace operation method according to the present embodiment, pulverized coal having a tensile breaking strength of 50 kPa or less is used as the pulverized coal 18 blown from the tuyere 38. As a result, even if the pulverized coal adheres to the inner wall of the pipe, the tensile breaking strength is low, so that the growth of the pulverized coal powder layer is suppressed, and the number of pipes blocked by the pulverized coal during the operation of the blast furnace can be reduced.

FIG. 2 is a schematic view illustrating a method for measuring tensile breaking strength. In the present embodiment, the tensile breaking strength is a pulverized coal powder produced by charging pulverized coal into a cell 50 composed of an upper cell 52 and a lower cell 54 and compressing the pulverized coal powder at a compressive stress of 4.0 MPa for 60 seconds. The strength (MPa) required for splitting the layer 56 by pulling the upper cell 52 and the pulverized coal powder layer 56 upward at a speed of 0.1 mm / sec while fixing the lower cell 54.

As shown in FIG. 2, the cell 50 has an upper cell 52 and a lower cell 54. The pulverized coal 18 is charged to the upper part in the cylindrical accommodating portion formed by combining the upper cell 52 and the lower cell 54. In the example shown in FIG. 2, the cross section of the accommodating portion formed by combining the upper cell 52 and the lower cell 54 is circular, and the inner diameter thereof is, for example, 20 mm.

The pulverized coal powder layer 56 compresses the pulverized coal 18 charged in the accommodating portion from above through the upper lid 58 at a rate of 0.1 mm / sec, and when the compressive stress reaches 4.0 MPa, the compressive stress thereof. It is produced by holding for 60 seconds while maintaining the above. With respect to the pulverized coal powder layer 56 produced in this manner, the upper cell 52 and the pulverized coal powder layer 56 are pulled upward at a speed of 0.1 mm / sec while the lower cell 54 is fixed, and the pulverized coal is used. The powder layer 56 is divided in the vertical direction. The maximum tensile strength required for this division is divided by the cross-sectional area of the pulverized coal powder layer 56 to calculate the tensile breaking strength.

Further, in the blast furnace operation method according to the present embodiment, instead of the pulverized coal having a tensile breaking strength of 50 kPa or less, the pulverized coal powder layer has a porosity of 0.35 or more. You may use it. Even if such pulverized coal is used, the growth of the pulverized coal powder layer can be suppressed, and the number of pipes blocked by the pulverized coal during operation can be reduced. Here, the porosity is the porosity of the pulverized coal powder layer produced by the same method as the measurement of the tensile breaking strength, and is a value calculated by the following formula (1).

ε = (ρ ₂ −ρ ₁ ) / ρ ₂ ... (1)

However, in the above formula (1), ε is the void ratio (-), and ρ ₁ ^{is the bulk density (kg / m 3} ) calculated from the volume (cross-sectional area x height) and mass of the pulverized coal powder layer. ), And ρ ₂ is the particle density (kg / m ³ ) of the pulverized coal particles. The height of the pulverized coal powder layer in terms of bulk density is the height after compression for 60 seconds with a compressive stress of 4.0 MPa. The particle density was measured using the vapor phase substitution method.

The pulverized coal used in the blast furnace operating method according to the present embodiment is preferably heat-treated pulverized coal. By heat-treating the pulverized coal, volatile components are released from the pulverized coal and the particle shape of the pulverized coal particles changes, which reduces the tensile breaking strength of the pulverized coal powder layer and the pulverized coal powder layer. Porosity is improved. Therefore, even if the pulverized coal powder layer grows on the inner wall of the pipe and blocks the pipe, the growth of the pulverized coal powder layer is suppressed by heat-treating the pulverized coal, and the growth of the pulverized coal powder layer is suppressed. It can be reformed into pulverized coal with suppressed clogging.

Next, the heat treatment effect of pulverized coal will be described. As the pulverized coal for evaluation, heat-treated coals C to F in which pulverized coal A, pulverized coal B, and pulverized coal B were heat-treated at 280 ° C., 300 ° C., 600 ° C., and 900 ° C. for 1 hour in a nitrogen atmosphere were prepared. The properties of each pulverized coal are shown in Table 1. In addition, d.b. of Table 1 shows that it is a dry base. For example, in the case of fixed carbon, (fixed carbon (wet base%) / (100-moisture)) x 100 = fixed carbon (dry base), and the fixed carbon (wet base%) is converted to fixed carbon (dry base%). it can.

Since some of the volatile components of the heat-treated coals C to F are released by the heat treatment, the volatile components are smaller than those of the pulverized coal B that has not been heat-treated. Further, the higher the temperature of the heat treatment, the smaller the volatile matter contained in the pulverized coal.

The particle size of each of the pulverized coals A and B and the heated pulverized coals C to F was adjusted using a sieve so that the harmonic mean particle size was 8 μm. The harmonic mean particle size was calculated by measuring the particle size distribution of pulverized coal using a wet particle size distribution measuring device by the laser diffraction scattering method, and using the volume ratio (volume%) at each particle size and the following formula (2). ..

D _p = Σn / Σ (n / d) ... (2)
However, in the above formula (2), D _p is the harmonic mean particle size (m), d is the particle size (m) of the pulverized coal, and n is the volume ratio (volume%).

The pulverized coal shown in Table 1 was charged into the accommodating portion of the cell 50 shown in FIG. 2, compressed at a rate of 0.1 mm / sec, and when the compressive stress reached 4.0 MPa, the compressive stress was maintained. A pulverized coal powder layer of each pulverized coal was prepared by holding the mixture for 60 seconds. The tensile strength at break and the porosity were measured using this pulverized coal pulverized coal layer. Table 2 shows the tensile strength at break and the porosity of each pulverized coal.

As shown in Table 2, the heat treatment reduced the tensile breaking strength of the pulverized coal powder layer and increased the porosity of the pulverized coal powder layer. By heat-treating the pulverized coal, volatile components are released from the pulverized coal and the particle shape of the pulverized coal is changed, which reduces the tensile breaking strength of the pulverized coal powder layer and the pulverized coal powder layer. It is probable that the porosity increased.

Focusing on the heat treatment temperature of the pulverized coal, the tensile breaking strength of the pulverized coal powder layer is remarkably lowered and the porosity of the pulverized coal powder layer is remarkably increased by setting the heat treatment temperature to 300 ° C. or higher. FIG. 3 is a graph showing the relationship between the heat treatment temperature of the pulverized coal B and the pulverized coal X having different properties from the pulverized coal B and the tensile breaking strength of the pulverized coal powder layer. As shown in FIG. 3, the tensile breaking strength of the pulverized coal powder layer heat-treated at 300 ° C. for both pulverized coal B and X is significantly lower than the tensile breaking strength of the pulverized coal powder layer heat-treated at 280 ° C. did. From this result, the heat treatment temperature of the pulverized coal is preferably 300 ° C. or higher, and the tensile breaking strength of the pulverized coal powder layer can be significantly reduced by the heat treatment at 300 ° C. or higher.

FIG. 4 is a graph showing the relationship between the heat treatment temperature of the pulverized coal B and the pulverized coal X having different properties from the pulverized coal B and the porosity of the pulverized coal powder layer. As shown in FIG. 4, the porosity of the pulverized coal powder layer heat-treated at 300 ° C. for both pulverized coal B and X was significantly higher than the porosity of the pulverized coal pulverized coal layer heat-treated at 280 ° C. From this result, the heat treatment temperature of the pulverized coal is preferably 300 ° C. or higher, and the porosity of the pulverized coal powder layer can be remarkably increased by the heat treatment at 300 ° C. or higher.

As described above, the heat treatment of the pulverized coal releases volatile components from the pulverized coal and changes the particle shape, which lowers the tensile breaking strength of the pulverized coal powder layer and increases the porosity. .. Since the release start temperature of the volatile matter from the pulverized coal is around 300 ° C., more volatile matter can be released from the pulverized coal by heat treatment at a temperature of 300 ° C. or higher, and as a result, the pulverized coal The tensile breaking strength of the powder layer was remarkably reduced, and the porosity of the pulverized coal powder layer was remarkably increased. On the other hand, if the heat treatment is performed at a temperature exceeding 1000 ° C., volatile components are not released from the pulverized coal. Therefore, the heat treatment temperature of the pulverized coal is preferably 1000 ° C. or lower.

For the purpose of confirming the change in the particle shape due to the heat treatment of the pulverized coal, the particle shape of each pulverized coal was observed using a microscope, and the circularity of each pulverized coal was calculated from the observation result. 10,000 particles were observed in each pulverized coal, and the circularity was calculated using the following formula (3). The closer the circularity is to 1, the closer the shape is to a true sphere.

K = 4πS / L ² ... (3)
However, in the equation (3), K is the circularity (−), S is the projected area (m ² ) of the particle, and L is the perimeter (m) of the particle.

FIG. 5 is a graph showing the relationship between the volatile content of pulverized coal and the circularity. As shown in FIG. 5, the pulverized coal A which has not been heat-treated has a low circularity even if the volatile content is as low as 15% by mass. On the other hand, although the pulverized coal B had a high volatile content of 48.3% by mass, the volatile content decreased and the circularity of the pulverized coal B increased when heat treatment was performed. Further, the higher the temperature of the heat treatment, the lower the volatile content of the pulverized coal and the higher the circularity of the pulverized coal. From these results, it is considered that by heat-treating the pulverized coal, the volatile components in the pulverized coal are expanded and released and the entire particles are also expanded, which increases the circularity of the pulverized coal.

FIG. 6 is a graph showing the relationship between the circularity of the pulverized coal and the porosity of the pulverized coal pulverized coal layer. As shown in FIG. 6, the higher the circularity of the pulverized coal B by heat treatment, the higher the porosity of the pulverized coal powder layer tended to be. It is considered that this is because the pulverized coal particles become spherical by the heat treatment, so that the entanglement between the pulverized coals is reduced, and as a result, the porosity of the pulverized coal powder layer is increased.

Next, the results of confirming the effect of suppressing pipe blockage by injecting the pulverized coal shown in Table 1 into the blast furnace and carrying out the operation will be described. Pulverized coal A shown in Table 1, with B and heating pulverized coal C to F, tuyere 38 present, pig iron production amount of the target 11500t / day in a blast furnace having an inner volume of 5000 m ³ comprising a pulverized coal transport pipes 76 present, The operation of the blast furnace for blowing pulverized coal into the blast furnace at a ratio of pulverized coal of 150 kg / t-pig iron was carried out for 5 days. Even if the pulverized coal transport pipes at each tuyere were blocked, the blockage was not resolved, and more pulverized coal than usual was transported to the unoccluded pipes, and the operation was performed so that the pulverized coal ratio was constant. Further, the particle size of the pulverized coal to be blown was adjusted as needed so that the harmonic mean diameter was constant at 8 μm. Table 3 shows the average number of obstructed transport pipes and the average coke ratio per day when each pulverized coal is blown.

As shown in Table 3, in the pulverized coals A and B and the heat-treated coal C, the number of closed pipes was 6 or more per day. On the other hand, in the heat-treated coals D to F, the number of pipes blocked was less than 1 / day, and the number of pipes blocked with pulverized coal during blast furnace operation was significantly reduced.

As shown in Table 2, the pulverized coals A and B and the heat-treated coal C in which the number of closed pipes is 6 or more are pulverized coals in which the tensile breaking strength of the pulverized coal pulverized coal layer is larger than 50 kPa. On the other hand, the heat-treated coals D to F in which the number of closed pipes is less than 1 / day are pulverized coals having a tensile breaking strength of 50 kPa or less in the pulverized coal pulverized coal layer. From these results, it is possible to suppress the growth of the pulverized coal powder layer in the piping by using pulverized coal having a tensile breaking strength of 50 kPa or less, thereby reducing the number of piping that is blocked by the pulverized coal during blast furnace operation. You can see that it can be reduced.

Next, focusing on the average coke ratio in the operation of the blast furnace carried out by blowing each pulverized coal, the average coke ratio was high when the pulverized coals A and B and the heat-treated coal C were blown, and the heat-treated coals D to F had a high average coke ratio. It can be seen that the average coke ratio is low at the time of blowing. When pulverized coal A, B, and heat-treated coal C are blown into the blast furnace, a deviation in the amount of pulverized coal blown in the circumferential direction of the blast furnace occurs due to the blockage of the piping, and the temperature in the peripheral direction of the blast furnace It is probable that the occurrence of deviation and the deterioration of the air permeability in the furnace resulted in an increase in the average coke ratio. On the other hand, it was confirmed that when the heat-treated coals D to F were blown in, the blockage of the pipe was suppressed, and thereby the increase in the average coke ratio in the blast furnace operation could be suppressed.

Further, as shown in Table 2, the pulverized coals A and B and the heat-treated coal C in which the number of closed pipes is 6 or more per day are pulverized coals in which the porosity of the pulverized coal pulverized coal layer is less than 0.35. Is. On the other hand, the heat-treated coals D to F in which the number of closed pipes is less than 1 / day are pulverized coals having a porosity of 0.35 or more in the pulverized coal pulverized coal layer. From these results, by using pulverized coal having a porosity of 0.35 or more in the pulverized coal pulverized coal layer, the growth of the pulverized coal powder layer in the piping can be suppressed, and as a result, the pulverized coal can be used during blast furnace operation. It can be seen that the number of pipes to be blocked can be reduced and the increase in the average coke ratio in blast furnace operation can be suppressed.

As described above, in the blast furnace operation method according to the present embodiment, pulverized coal having a tensile breaking strength of 50 kPa or less in the pulverized coal pulverized coal layer or pulverized coal having a porosity of 0.35 kPa or more in the pulverized coal pulverized coal layer is used. As a result, the growth of the pulverized coal powder layer in the pipes can be suppressed, and the number of pipes blocked by the pulverized coal during blast furnace operation can be reduced. By reducing the number of pipes to be closed, it is possible to suppress the occurrence of temperature deviation in the furnace circumferential direction in the blast furnace and the deterioration of the air permeability in the furnace, and it is possible to suppress the increase in the coke ratio due to the blockage of the pipes.

In this embodiment, an example of using heat-treated pulverized coal is shown, but the present invention is not limited to this. For example, heat-treated pulverized coal is mixed with unheat-treated pulverized coal, and the tensile breaking strength of the pulverized coal powder layer of the entire pulverized coal is 50 kPa or less, or the porosity is 0.35 or more. You may use it.

For example, the heat-treated heat-treated coals C to F may be blended with the heat-treated pulverized coal A. Table 4 shows the tensile strength at break and the porosity of the pulverized coal blended so that the pulverized coal A is 80% by mass, the pulverized coal B, or any one of the heat-treated coals C to F is 20% by mass. Shown in. In Table 4, "pulverized coal A + pulverized coal B" indicates pulverized coal containing 80% by mass of pulverized coal A and 20% by mass of pulverized coal B, and has the same meaning in the following rows. Is.

As shown in Table 4, by blending the heat-treated coals C to F, the tensile breaking strength of the pulverized coal pulverized coal layer of the entire pulverized coal is lowered, and the porosity of the pulverized coal powder layer is increased. Further, even if the pulverized coal A has a tensile breaking strength of the pulverized coal powder layer larger than 50 kPa, the pulverized coal can be mixed with the heat-treated coals E and F having a tensile breaking strength of 50 kPa or less. It was confirmed that the tensile breaking strength of the entire pulverized coal powder layer could be 50 kPa or less. Similarly, by blending pulverized coal A having a porosity of less than 0.35 in the pulverized coal powder layer with pulverized coal having a porosity of 0.35 or more in the pulverized coal powder layer, the entire pulverized coal is pulverized. It was confirmed that the porosity of the powder layer could be 0.35 or more.

Next, the results of confirming the pipe blockage suppressing effect using the pulverized coal shown in Table 4 will be described. Using pulverized coal as shown in Table 4, tuyeres 38 present, pig iron production amount of the target 11500t / day in a blast furnace having an inner volume of 5000 m ³ with pulverized coal transport pipes 76 present in the pulverized coal ratio of 150 kg / t-pig iron The operation of the blast furnace, which blows pulverized coal into the blast furnace, was carried out for 5 days. Even if the pulverized coal transport pipes at each tuyere were blocked, the blockage was not resolved, and more pulverized coal than usual was transported to the unoccluded pipes, and the operation was performed so that the pulverized coal ratio was constant. Further, the pulverization conditions were adjusted as needed so that the particle size of the pulverized coal to be blown was constant at a harmonic mean diameter of 8 μm. Table 5 shows the average number of obstructed transport pipes and the average coke ratio per day when each pulverized coal is blown.

As shown in Table 5, in the pulverized coal A + pulverized coal B, the pulverized coal A + the heat-treated coal C, and the pulverized coal A + the heat-treated coal D, the number of closed pipes was 7 or more per day. On the other hand, in the pulverized coal A + heat-treated coal E and the pulverized coal A + heat-treated coal F, the number of pipes blocked was less than 1 / day, and the number of pipes blocked by pulverized coal during blast furnace operation was significantly reduced.

As shown in Table 4, the pulverized coal A + pulverized coal B, the pulverized coal A + the heat-treated coal C, and the pulverized coal A + the heat-treated coal D in which the number of pipes blocked is 7 / day or more are the pulverized coal of the whole pulverized coal. It is a pulverized coal having a tensile breaking strength of a powder layer of more than 50 kPa. Further, the pulverized coal A + heat-treated coal E and the pulverized coal A + heat-treated coal F in which the number of closed pipes is less than 1 / day are pulverized powders having a tensile breaking strength of 50 kPa or less in the pulverized coal powder layer of the entire pulverized coal. It is charcoal. Based on these results, pulverized coals having a tensile breaking strength of more than 50 kPa and pulverized coal having a tensile breaking strength of 50 kPa or less are mixed so that the tensile breaking strength of the pulverized coal powder layer of the entire pulverized coal is 50 kPa or less. It can be seen that the use of charcoal can suppress the growth of the pulverized coal powder layer in the pipes, thereby reducing the number of pipes blocked by the pulverized coal during blast furnace operation.

Focusing on the average coke ratio in the operation of the blast furnace carried out by injecting each pulverized coal, the average coke ratio at the time of injecting pulverized coal A + pulverized coal B, pulverized coal A + heat-treated coal C, and pulverized coal A + heat-treated coal D is It can be seen that the average coke ratio is low when the pulverized coal A + heat-treated coal E and the pulverized coal A + heat-treated coal F are blown. When pulverized coal A + pulverized coal B, pulverized coal A + heat-treated coal C, and pulverized coal A + heat-treated coal D are injected, a deviation in the amount of pulverized coal injected in the circumferential direction of the blast furnace occurs due to the blockage of the pipe. It is probable that the occurrence of temperature deviation in the circumferential direction of the blast furnace and the deterioration of the air permeability in the furnace resulted in an increase in the average coke ratio. On the other hand, it was confirmed that when the pulverized coal A + heat-treated coal E and the pulverized coal A + heat-treated coal F were blown in, the blockage of the pipe was suppressed, and the increase in the average coke ratio due to the blockage of the pipe could be suppressed.

Further, as shown in Table 4, the pulverized coal A + pulverized coal B, the pulverized coal A + the heat-treated coal C, and the pulverized coal A + the heat-treated coal D in which the number of pipes blocked is 7 / day or more are the whole pulverized coal. The pulverized coal is a pulverized coal having a porosity of less than 0.35 in the powder layer. The pulverized coal A + heat-treated coal E and the pulverized coal A + heat-treated coal F are pulverized coal having a porosity of 0.35 or more in the pulverized coal pulverized coal layer. Therefore, the pulverized coal having a porosity of less than 0.35 is mixed with the pulverized coal having a porosity of 0.35 or more so that the porosity of the pulverized coal powder layer of the entire pulverized coal is 0.35 or more. By using pulverized coal, the growth of the pulverized coal powder layer in the pipes is suppressed, which can reduce the number of pipes blocked by pulverized coal during blast furnace operation and increase the average coke ratio due to the blockage of the pipes. It was confirmed that it could be suppressed.

10 coal 12 coal hopper 14 feeder 16 pulverized coal production equipment 18 pulverized coal 20 main pipe 22 bug filter 24 coal bin 26 blow tank 28 distributor 30 branch pipe 32 blow pipe 34 blast furnace 36 lance 38 tuyere 40 hot air furnace 50 cell 52 upper cell 54 Lower cell 56 Fine coal powder layer 58 Top lid

Claims (4)

It is a blast furnace operation method in which pulverized coal having a particle size distribution of 60 mass% ≤ -74 μm is blown from the blast furnace tuyere.
A method for operating a blast furnace, in which crushed coal is used as a raw material, pulverized coal having a porosity satisfying the following range is selected, and the selected pulverized coal is blown into the blast furnace.
Record
The porosity of the pulverized coal powder layer, which is charged into a cell composed of an upper cell and a lower cell and is produced by compressing with a compressive stress of 4.0 MPa for 60 seconds, is 0.35 or more. The method for operating a blast furnace according to claim 1 , wherein the pulverized coal is heat-treated pulverized coal. The blast furnace operating method according to claim 2 , wherein the pulverized coal is pulverized coal that has been heat-treated at 300 ° C. or higher. The blast furnace operating method according to claim 1, wherein the blast furnace is a mixture of heat-treated pulverized coal and non-heat-treated pulverized coal.

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