Operating method of blast furnace and pulverized coal for injection into blast furnace

Abstract

To provide an operation method for a blast furnace capable of preventing a high coke ratio by preventing blockage of piping by blowing pulverized coal with improved transportability in advance into the blast furnace, and to provide pulverized coal for blowing into the blast furnace.SOLUTION: In an operation method for a blast furnace in which pulverized coal is blown into the blast furnace along with the blast from a tuyere, the pulverized coal for blowing into the furnace is first supplied to a cyclone with an electric field formed inside, and a voltage is applied to the cyclone. Then, the saturated charge amount of the pulverized coal is measured with a potential measurement instrument installed at the outlet of the cyclone to evaluate its conveyability. Subsequently, the pulverized coal is blown into the furnace through the tuyere of the blast furnace.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for operating a blast furnace and pulverized coal for blowing into a blast furnace, which uses pulverized coal with improved transportability as the pulverized coal when blowing pulverized coal from the tuyere into the furnace.

Background Art

[0002] In recent years, global warming due to an increase in carbon dioxide emissions has become a problem, and suppressing CO2 emissions has also become an important issue in the iron and steel industry. For this reason, in recent blast furnace operations, low reduction agent ratio (low RAR: Reduction Agent Rate) operations, that is, operations with a small total amount of reduction agents (pulverized coal) blown from the tuyere and coke charged from the top of the furnace when producing 1 t of pig iron, are recommended.

[0003] In general, a blast furnace mainly uses coke charged from the top of the furnace and pulverized coal blown from the tuyere as reduction agents. In the operation of this blast furnace, in order to achieve low reduction agent ratio operation and suppression of carbon dioxide emissions, as one method, a measure to reduce the coke ratio by blowing pulverized coal into the tuyere under the condition that there are as few operation troubles as possible is considered effective.

[0004] Generally, pulverized coal is pneumatically transported through pipes and finally blown into the blast furnace through the tuyere. At this time, the transportability of the pulverized coal varies greatly depending on differences in the brand and particle size of the pulverized coal. As a result, the pulverized coal adheres to the inside of the pipe during pneumatic transport, the pipe becomes blocked, the air permeability in the blast furnace deteriorates, the temperature drops, and the coke ratio may increase. In order to solve such problems of the transportability of pulverized coal, various methods have been proposed conventionally.

[0005] For example, in Patent Document 1, as a method for injecting pulverized coal into the blast furnace, there is a particle size distribution measurement step of taking out the pulverized coal produced by a pulverized coal manufacturing device from a transport path and periodically measuring it with a particle size distribution measuring device, and a pulverizing force adjustment step of adjusting the coal pulverizing force in the pulverized coal manufacturing device using the deviation between the measured value and the target value measured in the particle size distribution measurement step. The particle size distribution measurement step discloses a method using a particle size distribution measuring device in which the standard deviation of the measured values of the standard sample is within 1%. The particle size distribution of the 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, and a method of injecting pulverized coal pulverized so that the particle size distribution of the pulverized coal is "45% ≤ -44 μm ratio (%) ≤ 50%, 60% ≤ -74 μm ratio (%)" is proposed.

[0006] In addition, in Patent Document 2, regarding the pneumatic transport method of pulverized coal, focusing on the interparticle adhesion force of pulverized coal as an index other than particle size, a method of injecting pulverized coal with an interparticle adhesion force value calculated based on Rumpf's formula of 3.26×10 -7 N or less into the blast furnace is proposed.

[0007] In addition, in Patent Document 3, pulverized coal is charged into a cell composed of an upper cell and a lower cell, the cell is compressed at a pressure of 4.0 MPa for 60 seconds to produce a pulverized coal powder layer, and then, while the lower cell is fixed, the upper cell and the pulverized coal powder layer are pulled upward at a speed of 0.1 mm / sec and separated, and a method of injecting pulverized coal with a tensile fracture strength required at that time of 50 kPa or less into the blast furnace is proposed.

[0008] In addition, in Patent Document 4, 27 Al or 29 the nuclear magnetic resonance spectrum of Si is measured, the chemical form of the inorganic minerals mainly composed of Al and Si present in the coal is classified based on the measurement result, and a method of evaluating the transportability of the coal (pulverized coal) based on the classification is proposed.

[0009] Further, Patent Document 5 proposes a method of adding a pulverized coal transportability improver composed of an inorganic salt soluble in water to pulverized coal in order to improve the transportability of the pulverized coal blown from the tuyere of a metallurgical furnace or a sintering furnace.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0011] In the method disclosed in Patent Document 1, regardless of the coal brand, the particle size distribution of the pulverized coal is adjusted so that "45% ≤ ratio (%) of - 44μm ≤ 50%, 60% ≤ ratio (%) of - 74μm" to attempt to prevent blockage of the pipe leading to the blast furnace. However, in actual operation, even if the particle size distribution is adjusted, as shown in Fig. 6, there are some cases where the blockage frequency of the pipe is high depending on the coal brand, and there is a problem that the number of blockages actually increases.

[0012] Further, in the method disclosed in Patent Document 2, the coal brand to be used is selected based on the value of the interparticle adhesion force according to Rumpf's formula. However, when the pipe is blocked, the pulverized coal forms a powder layer and adheres to the pipe. Therefore, when the particle size of the pulverized coal changes or the porosity of the powder layer of the pulverized coal changes, there is a problem that the tensile fracture strength of the powder layer of the pulverized coal changes and the pipe is blocked. Also, in actual operation, even if a brand with a low interparticle adhesion force is selected, as shown in Fig. 7, there are cases where the blockage frequency of the pipe is high.

[0013] Also, in the method disclosed in Patent Document 3, a pulverized coal powder layer created by compressing at a pressure of 40 MPa for 60 seconds is pulled and fractured, and the coal brand to be used is selected based on the value of the tensile fracture strength required at that time. However, in actual operation, since the pulverized coal is flowing in the pipeline, there is a problem in evaluating the transportability of the pulverized coal from the tensile fracture strength of the stationary powder layer as described above.

[0014] Also, in the method disclosed in Patent Document 4, the nuclear magnetic resonance spectrum of Al or Si present in the pulverized coal is measured, and the transportability of the pulverized coal is evaluated from the measurement results. However, since the nuclear magnetic resonance spectrometer is a very expensive and delicate facility, it is difficult to use it for the operation of an actual machine in which the brand used and the injection amount are changed according to the conditions inside the blast furnace. Also, in this method, although the chemical form of the inorganic minerals mainly composed of aluminum and silicon is quantitatively carried out, the final evaluation of the transportability is qualitative according to the abundance ratio, so there is a problem that it is difficult to say that it is a highly general method. 27 Al or 29 Si is measured, and the transportability of the pulverized coal is evaluated from the measurement results. However, since the nuclear magnetic resonance spectrometer is a very expensive and delicate facility, it is difficult to use it for the operation of an actual machine in which the brand used and the injection amount are changed according to the conditions inside the blast furnace. Also, in this method, although the chemical form of the inorganic minerals mainly composed of aluminum and silicon is quantitatively carried out, the final evaluation of the transportability is qualitative according to the abundance ratio, so there is a problem that it is difficult to say that it is a highly general method.

[0015] Also, in the method disclosed in Patent Document 5, while an improvement in transportability is expected by reducing the triboelectric charge amount of the pulverized coal, the added inorganic salts may act as a factor interfering with the stable operation of the blast furnace due to the deterioration of air permeability accompanying the increase in powder ratio in the lower part of the blast furnace. Also, when these inorganic salts melt, the total amount of molten slag staying in the furnace increases, and there is also a concern about the deterioration of air permeability accompanying the narrowing of the gas path in the lower part of the furnace. These problems can be addressed by increasing the amount of coke used as a gas path in the furnace, but this leads to a deterioration in the hot metal cost. Also, there is a need to increase the reduction material ratio in the blast furnace by the amount of heat required for the temperature rise and melting of the inorganic salts, and there is a concern about an increase in the CO2 emissions from the blast furnace. Therefore, this method has a problem that there are many demerits in the blast furnace body compared to the effects obtained by improving the transportability of the pulverized coal.

[0016] The present invention has been made in view of the problems of each of the above prior arts, and its object is to prevent clogging of pipes and suppress an increase in the coke ratio by blowing pulverized coal with improved transportability in advance into a blast furnace, and to propose an operation method of a blast furnace and pulverized coal for blowing into the blast furnace.

Means for Solving the Problems

[0017] As a result of intensive studies to solve such problems, the inventors focused on the fact that the electrostatic force of the pulverized coal causes adhesion and blockage to the transport pipe during the process of transporting the pulverized coal to the blast furnace, and found that the transportability can be evaluated by the saturation charge amount of the pulverized coal, and thus developed the present invention.

[0018] The present invention has been made based on the above findings, and its gist is as follows. That is, the present invention is an operation method of a blast furnace in which pulverized coal is blown into the furnace of the blast furnace in accordance with the blast from the tuyere. First, the pulverized coal to be blown into the furnace is supplied to a cyclone that forms an electric field inside, a process of applying a voltage is performed in the cyclone, and the transportability is evaluated by measuring the saturation charge amount of the pulverized coal with a potential measuring device installed at the discharge port of the cyclone, and then it is blown from the tuyere of the blast furnace into the furnace.

[0019] Further, in the operation method of the blast furnace of the present invention, (1) The pulverized coal showing transportability suitable for blowing has a saturation charge amount of 400 nC / g or less when measured with a potential measuring device installed at the discharge port of the cyclone, (2) The pulverized coal is dried, (3) The drying treatment of the pulverized coal is performed by heating to a temperature of 100°C or higher, is preferable.

[0020] In addition, the pulverized coal for injection into a blast furnace according to the present invention is obtained by applying a voltage in a cyclone in which an electric field is formed inside, and the saturated charge amount measured by a potential measuring device installed at the discharge port of the cyclone is 400 nC / g or less.

[0021] In the pulverized coal for injection into a blast furnace according to the present invention, (1) the pulverized coal is dried, (2) the pulverized coal is dried at a temperature of 100°C or higher, which is preferable.

Advantages of the Invention

[0022] According to the present invention, by injecting pulverized coal whose transportability has been evaluated in advance from the tuyere of the blast furnace into the furnace, it becomes possible to operate the blast furnace while suppressing blockage of the piping due to the characteristics of the pulverized coal itself. Therefore, it becomes possible to suppress deterioration of the air permeability and a decrease in temperature inside the blast furnace, and it is possible to effectively suppress an increase in the coke ratio and the like.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0024] Hereinafter, the operation method of the blast furnace according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a blast furnace used for carrying out the operation method of the blast furnace according to the present invention and its auxiliary equipment. The method of blowing pulverized coal into the furnace of the blast furnace from the tuyere will be described with reference to FIG. 1.

[0025] The coal 1 stocked in the yard is stored in the coal hopper 2 and then cut out by the feeder 3 to the pulverized coal manufacturing device 4. In the pulverized coal manufacturing device 4, the coal 1 is pulverized and dried, and then adjusted to pulverized coal 5 of a predetermined particle size.

[0026] The pulverized coal 5 adjusted in this way is pneumatically conveyed to the bag filter 7 through the main pipe 6. The pulverized coal 5 collected by the bag filter 7 is stored in the coal bin 8 and then transported to the blowing tank 9. The pulverized coal 5 transported to the blowing tank 9 is supplied to the distributor 10 by pneumatic conveyance, and further distributed from the distributor 10 to each tuyere 14 disposed at the lower part of the blast furnace 13 through a plurality of branch pipes 11 and blow pipes 12. Incidentally, the pulverized coal 5 is injected into the hot air supplied to the blow pipe 12 connected to each tuyere 14 from the hot blast stove 15, and is blown into the blast furnace 13 from the tuyere 14 together with the hot air. The operation of the blast furnace 13 is carried out in this way.

[0027] As described above, the pulverized coal 5 is blown into the blast furnace 13 from the tuyere 14 through several piping systems, namely pipes, valves, holders, etc. and blowing devices. When a large amount of pulverized coal 5 is blown into the blast furnace 13 in this way, a part of the pulverized coal 5 may adhere to the inside of the piping system or the like, and the powder layer of the adhered pulverized coal 5 may grow and the pipe may be blocked, making it impossible to continue normal blast furnace operation. Therefore, when blowing the pulverized coal 5 into the furnace of the blast furnace 13, it is strongly required to ensure that the pulverized coal 5 flows smoothly without adhering to the piping system or causing blockage (improvement of transportability).

[0028] As a cause of the pulverized coal 5 adhering to each pipe, some adhesion force must act between the pulverized coal 5 and the pipe. Classifying this adhesion force by form, the existence of van der Waals force, liquid bridge force, and electrostatic force is considered.

[0029] First, the van der Waals force is an intermolecular force acting between atoms, ions, and molecules, and its origin lies in the dispersion force between electric dipoles derived from the non-steady bias of the electron distribution within the molecule. Since the acting force is isotropic and inversely proportional to the seventh power of the interatomic distance, this force is extremely small when the pulverized coal 5 and the pipe are not in contact. However, although this van der Waals force may act significantly during the process of forming a powder layer by the pulverized coal 5 adhering to the piping system or the like, it is considered not to be the fundamental cause of the adhesion of the pulverized coal 5 to the piping system or the like.

[0030] Next, the liquid bridging force is the attractive force acting between particles when a liquid exists in the gas phase and the liquid is retained between the particles, and physically can be explained as the surface tension in the liquid bridge having uneven curved surfaces. Although this liquid bridging force varies depending on the shape of the bridge, the surface roughness of the particles, the water absorption state, and the impurity concentration in the adsorbed water, it is said to act significantly as an adhesive force in an environment with a relative humidity of 60% or more. On the other hand, inside the blow pipe 12 connected to the tuyere 14 of the blast furnace 13, the conveying environment of the pulverized coal 5 is at a temperature of about 100°C and a conveying air flow of about 20 m / s, and the relative humidity is extremely low. Therefore, it is considered that this liquid bridging force does not cause the adhesion of the pulverized coal 5 to the piping system or the like.

[0031] On the other hand, the electrostatic force is the force acting between charged particles, and its value is proportional to the product of the respective charges and inversely proportional to the square of the distance between the charges. While the van der Waals force is inversely proportional to the seventh power of the interparticle distance, the electrostatic force is a force inversely proportional to the square of the distance. Therefore, even if the pipe and the particles are not in contact, there is a high possibility that a significant force acts upon contact. Also, although the blow pipe 12 connected to the tuyere 14 of the blast furnace 13 is usually grounded and thus the electrostatic force is considered not to act, in reality, it is known that an electrostatic force called the electric image force also acts between an uncharged object and charged particles. This is an attractive force generated by free electrons in the uncharged object being attracted by the charge of the charged particles. Therefore, it is considered extremely likely that the electrostatic force is the cause of the adhesion of the pulverized coal 5 during the conveying process to the blast furnace 13.

[0032] Based on the above, in the present invention, attention is paid to the electrostatic force during the conveying process of the pulverized coal 5 to the blast furnace 13, and it is concluded that it is effective to evaluate the transportability based on the saturation charge amount of the pulverized coal 5 blown into the furnace from the tuyere 14 of the blast furnace 13.

[0033] Therefore, an examination was conducted on the saturation charge amount of the pulverized coal 5 blown into the furnace of the blast furnace. Figure 2 is a schematic diagram showing a method for measuring the saturation charge amount of fine coal 5. In the present invention, the saturation charge amount of fine coal 5 means that fine coal 5 is introduced together with a carrier gas flow 18 into a cyclone 19 to which a voltage is applied, and the fine coal 5 is collected by a Faraday gauge 23 installed at the discharge part of the cyclone 19, and the maximum value (nC / g) of the charge amount measured by an electrometer 24 connected to the Faraday gauge 23. The voltage applied to the cyclone 19 is a voltage at which the fine coal 5 reaches at least the saturation charge amount, and is preferably in the range of -1 to 1 kV.

[0034] As shown in Figure 2, the cyclone 19 has an external electrode 20 and an internal electrode 21, and a voltage is applied to the internal electrode 21 by a high voltage generator 22. Thereby, an electric field is formed inside the cyclone 19, and the fine coal 5 is charged by passing through the electric field.

[0035] In the embodiments described below, fine coals A, B, C, D, E, F, and G were prepared as the fine coal for evaluation. Each of the fine coals A to G was adjusted in particle size so that the harmonic mean particle size was 15 to 20 μm. The harmonic mean particle size was calculated using a wet particle size distribution measuring device based on the laser diffraction scattering method to measure the particle size distribution of the fine coals A to G and using the volume ratio (volume%) at each particle size and the following formula (1). Dp = Σn / Σ(n / d) ··· (1) However, in the above formula (1), Dp is the harmonic mean particle size (μm), d is the particle size of the fine coal (μm), and n is the volume ratio (volume%).

[0036] In the implementation, each of the fine coals A to G was introduced into the cyclone 19 and charged by passing through the electric field formed in the cyclone 19, and the saturation charge amount was measured. The measurement was performed by changing the voltage applied to the internal electrode 21 of the cyclone 19 in increments of 0.2 kV until the charge amount reached saturation.

[0037] Regarding the relationship between the applied voltage to the cyclone 19 and the charge amount of the pulverized coal 5, taking pulverized coal A as an example, it will be described based on Fig. 3. As shown in this Fig. 3, it can be seen that the charge amount of pulverized coal A has an approximately odd function relationship with the applied voltage. Also, since the charge amount when the applied voltage is 0 kV fluctuates slightly to a positive value, it was also found that pulverized coal A has a tendency to be easily charged with positive charges. And the charge amount of pulverized coal A converges to an approximately constant value when the absolute value of the applied voltage becomes about 0.5 kV or more. From these results, it was found that pulverized coal A was charged until it reached the saturation charge amount inside the cyclone 19 to which a voltage of 0.5 kV or more in absolute value was applied. Note that there is a slight difference in the saturation charge amount between the case where the applied voltage is positive and the case where it is negative, but the maximum value in absolute value was taken as the saturation charge amount. Also, regarding pulverized coals B to G, it was found that when the applied voltage is applied in the range of -1 to 1 kV inside the cyclone 19, they are charged until they reach the saturation charge amount. The following Table 1 shows the saturation charge amounts of pulverized coals A to G.

[0038]

Table 1

[0039] Next, in order to estimate the charge amounts of each of the pulverized coals A to G in the actual machine's conveying line, a measurement test of the charge amounts of each of the pulverized coals A to G was conducted in a test system that simulated the actual machine's conveying line. Fig. 4 is a schematic diagram of the test system for estimating the charge amounts of pulverized coals A to G in the actual machine. Each of the pulverized coals A to G used in the test was first loaded into the Faraday gauge 25, and its initial charge amount was measured with the electrometer 26. After measuring the initial charge amount of the pulverized coals A to G, they were entrained in the compressed air 29 (the temperature was set to 100 °C and the speed was set to 20 m / s according to the actual machine.) and passed through a 1 m long pipe 30. Note that a stainless steel pipe with a diameter of 34 mm was used for the pipe 30. It was confirmed that the pulverized coals A to G were charged due to friction between particles and with the inner wall of the pipe 30 during passing through the pipe 30.

[0040] Next, pulverized coals A to G were collected by a Faraday gauge 31 installed at the outlet of the pipe 30, and the charge amount was measured by an electrometer 32 connected to the Faraday gauge 31. From the difference between the initial charge amounts of pulverized coals A to G measured by the electrometer 26 and the charge amounts of pulverized coals A to G after passing through the pipe 30 measured by the electrometer 32, the charge amount per unit transport distance (nC / g·m) of pulverized coals A to G passing through the pipe 30 was determined.

[0041] Next, from the charge amount per unit transport distance (nC / g·m) of pulverized coals A to G measured in the test system shown in FIG. 4 and the saturation charge amount (nC / g) of pulverized coals A to G measured in FIG. 2, the critical transport distance (m) of pulverized coals A to G until the saturation charge amount was reached was estimated.

[0042] Table 2 shows the charge amount per unit transport distance (nC / g·m) of pulverized coals A to G and the critical transport distance (m) until the saturation charge amount is reached, together with the saturation charge amount (nC / g). From the results shown in this Table 2, it was speculated that all of the pulverized coals A to G reached the saturation charge amount at a transport distance of 10 m or less.

[0043]

Table 2

[0044] Considering from the results of Table 2 that the transport line of pulverized coal in the actual machine is on the order of several hundred meters, it is speculated that in the operation of the actual machine, the pulverized coal reaches the saturation charge amount at the initial position (within 10 m) of the transport line. Therefore, using this saturation charge amount of the pulverized coal as an index, the influence of the electrostatic force of the pulverized coal on the adhesion to the piping system, etc. in the transport line of the actual machine was examined.

[0045] Based on the above examination results, the saturation charge amount of the pulverized coal and the transportability of the pulverized coal were verified using the actual machine. In order to confirm the influence of the saturation charge amount of the pulverized coal in the actual machine, for each of the pulverized coals A to G shown in Table 1 and Table 2, these were blown into the blast furnace for operation, and the correlation between the clogging property of the pipe and the saturation charge amount of the pulverized coal was investigated.

[0046] The actual machine used had an internal volume of 4,300 m, 34 tuyeres and 68 pulverized coal transport pipes. 3 The blast furnace was operated for five days with a lump coke rate of 280 kg / t, a small coke rate of 70 kg / t, and a target pig iron production of 10,000 t / day, with pulverized coal injected at a unit rate of 200 kg / t. Even if the pulverized coal transport pipe was clogged, the blockage was not cleared, and more pulverized coal than usual was transported to the unblocked pipe, so that the pulverized coal ratio remained constant. The grinding conditions were adjusted as needed to ensure that the particle size of the injected pulverized coal was 15 to 20 μm in harmonic mean particle size.

[0047] Figure 5 shows the average number of transport pipes clogged by adhesion of pulverized coal per day for each saturated charge of pulverized coal A to G. When pulverized coal C, D, and E, which had a saturated charge of 500 nC / g or more, were used, the average number of clogged transport pipes per day was 7 to 10, whereas when pulverized coal A, B, F, and G, which had a saturated charge of 400 nC / g or less, were used, the average number of clogged transport pipes per day was significantly reduced to 1 or less.

[0048] These results confirmed that, in blast furnace operations, by using pulverized coal with a saturated charge of 400 nC / g or less as the pulverized coal to be injected into the furnace, it is possible to reliably suppress the adhesion of pulverized coal to piping systems, etc., and to reduce the number of pipes that become clogged due to the adhesion of pulverized coal during blast furnace operations.

[0049] Therefore, when operating a blast furnace, the saturated charge of the pulverized coal to be injected into the blast furnace is measured, and pulverized coal having a saturated charge of 400 nC / g or less, preferably 360 nC / g or less is used. This prevents the pulverized coal from adhering to the transport piping, and prevents deviations in the amount of gas and temperature around the periphery of the blast furnace and deterioration of the gas permeability inside the furnace, thereby preventing an increase in the coke rate due to blockage of the piping.

[0050] In the present invention, it is preferable to use pulverized coal that has been heated and dried. By performing the heat treatment, volatile components are released from the pulverized coal, and even if it adheres to the pipe, its growth is suppressed (modified), so that blockage of the pipe can be effectively suppressed.

[0051] Also, for the drying treatment of the pulverized coal, the heating temperature is preferably 90°C or higher, more preferably 100°C or higher. By performing the drying treatment of the pulverized coal, it is possible to expect a reduction in the liquid bridging force due to the evaporation of the adhering moisture on the particle surface, and prevent pipe clogging.

[0052] As described above, the embodiments of the present invention have been explained. However, this embodiment forms a part of the disclosure of the present invention, and the present invention is not limited by these explanations and drawings. That is, all other embodiments, examples, and operation techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

Industrial Applicability

[0053] The present invention can be applied not only to the method of blowing pulverized coal into a blast furnace but also as a technology for conveying pipes for the same type of powder and granular materials other than pulverized coal.

Explanation of Signs

[0054] 1 Coal 2 Coal Hopper 3 Feeder 4 Pulverized Coal Manufacturing Apparatus 5 Pulverized Coal 6 Main Pipe 7 Bag Filter 8 Coal Bin 9 Blowing Tank 10 Distributor 11 Branch Pipe 12 Blow Pipe 13 Blast Furnace 14 Tuyere 15 Stove 18 Conveying Airflow 19 Cyclone 20 External electrode 21 Internal electrode 22 High voltage generator 23 Faraday gauge 24 Electrometer 25 Faraday gauge 26 Electrometer 29 Compressed air 30 Pipe 31 Faraday gauge 32 Electrometer

Claims

1. In the operation method of a blast furnace in which pulverized coal is blown into the blast furnace in accordance with the blast from the tuyere in the furnace, first, the pulverized coal having a harmonic average particle size of 15 to 20 μm to be blown into the furnace is supplied to a cyclone formed with an electric field inside, and a voltage of -1 to 1 kV is applied by passing through the electric field. Then, after evaluating the transportability by measuring the saturation charge amount of the pulverized coal with a potential measuring device installed at the discharge port of the cyclone, the pulverized coal having a saturation charge amount of 400 nC / g or less, which exhibits suitable transportability for blowing, is blown into the furnace from the tuyere of the blast furnace. The operation method of the blast furnace is characterized by this.

2. The operation method of the blast furnace according to Claim 1, wherein the pulverized coal is dried.

3. The operation method of the blast furnace according to Claim 2, wherein the drying treatment of the pulverized coal is performed by heating to a temperature of 100°C or higher.

4. Pulverized coal blown into the blast furnace in accordance with the blast from the tuyere in the furnace, the pulverized coal has a harmonic average particle size of 15 to 20 μm, and when a voltage of -1 to 1 kV is applied in a cyclone formed with an electric field inside, the saturation charge amount measured with a potential measuring device installed at the discharge port of the cyclone is 400 nC / g or less. The pulverized coal for blowing into the blast furnace is characterized by this.

5. The pulverized coal for blowing into the blast furnace according to Claim 4, wherein the pulverized coal is dried.

6. The pulverized coal for blowing into the blast furnace according to Claim 5, wherein the pulverized coal is dried at a temperature of 100°C or higher.

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