JP4093198B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method of operating a blast furnace for reducing the amount of reducing material used, and more specifically, while blowing pulverized coal, charging coke having a high reactivity index and sintered ore having a high reducibility index, The present invention relates to a method of operating a blast furnace that operates with a reduced amount of slag.

The technology for improving the reaction efficiency of the blast furnace and reducing the amount of reducing material used is an important issue not only for the reduction of pig iron production cost but also for the recent CO ₂ gas reduction problem.

  In blast furnace operation, sintered ore, pellets, lump ore, etc. (hereinafter collectively referred to as “ore”) as an iron source, and coke as a reducing material and fuel are alternately charged from the top of the furnace, Hot air is blown from the lower tuyere and auxiliary fuel such as pulverized coal is blown. The ore and coke charged from the top of the furnace form alternately stacked ore and coke layers, and the ore and coke in the blast furnace (hereinafter collectively referred to as “charge”) are unloaded. Therefore, while gradually descending the blast furnace toward the lower part of the blast furnace, the gas is heated by the gas rising from the lower part of the furnace and the temperature is raised.

Generally, in the blast furnace, when the temperature of the charge charged from the top of the furnace reaches around 500 ° C., ore gas reduction starts, and the ore becomes wustite (FeO) before reaching the temperature range of 900 to 1000 ° C. Reduced. As the temperature of the charge rises, the temperature difference between the charge and the gas decreases, and in the vicinity of 900 to 1000 ° C., the temperature difference and the temperature gradient in the furnace height direction become smaller, and ore gas reduction stagnates. It is known that a so-called “thermal preservation zone region” is formed. Then, as the temperature rises further, the ore gas reduction reaction (FeO + CO → Fe + CO ₂ ) and the coke solution loss reaction (C + CO ₂ → 2CO) both proceed actively to promote the reduction of the ore and produce reduced iron At the same time, dissolution and carburization of the produced reduced iron proceeds and pig iron is produced.

In the above heat conservation zone region, the coexisting phase of iron (Fe) -wustite (FeO) is in a state close to a reduction equilibrium (FeO + CO = Fe + CO ₂ ) depending on the oxygen potential of the gas rising in the furnace. It is believed that the ore gas reduction is stagnant.

An operation method using coke having high reactivity is known in order to recover and accelerate the reduction reaction of the ore by removing the state close to the reduction equilibrium. That is, coke that is highly reactive in the heat preservation zone region is used to promote the solution loss reaction (C + CO ₂ → 2CO), and the CO concentration in the gas rising in the furnace is increased to promote the ore reduction reaction. Is the method. Examples of the operation method for promoting the reduction reaction using highly reactive coke include the methods disclosed in Patent Literature 1 and Patent Literature 2 below.

  In Patent Document 1, in an operating method of a blast furnace in which an iron source mainly composed of sintered ore, ordinary metallurgical coke, and JIS reactivity is 30% or more and high-reactivity coke having an average particle size of 25 mm or less is charged, A method of operating a blast furnace is disclosed in which the temperature of the heat preservation zone in the blast furnace is controlled by adjusting at least one of the use ratio, particle size, and JIS reactivity of the highly reactive coke according to the reducibility of the sintered ore. ing. Moreover, in patent document 2, in the method disclosed in the above-mentioned patent document 1, a block iron ore having 3% or more of crystal water is further added as an iron source, and as one of the adjustment factors of the heat preservation zone temperature. In addition, an operation method including the use ratio of the lump ore is disclosed.

  However, when the coke reactivity is increased, the mass of coke is reduced by the gasification reaction, the coke substrate is weakened and the strength as particles is reduced, and the powder is reduced by load, impact, friction, etc. in the blast furnace. There is a risk that the air permeability in the blast furnace will deteriorate and the furnace condition will deteriorate.

JP-A-6-145730 (Claims and paragraph [0008])

Japanese Patent No. 3061965 (Claims and paragraph [0008]) JP-A-9-170008 (Claims and paragraph [0010]) Yuji Iwanaga: “Iron and Steel” Vol. 77 (1991) No. 1 p71-78

  The present invention has been made in view of the above problems, and the problem is that in the operation method of a blast furnace in which the amount of reducing material used in the blast furnace is reduced by using highly reactive coke, the cold strength of the coke is reduced. Providing a method for operating a blast furnace that suppresses coke strength deterioration and pulverization in the blast furnace, ensures air permeability in the furnace, and enables stable operation without increasing pig iron production costs There is.

  In order to solve the above-mentioned problems, the present inventors, based on the conventional problems, have a temperature rising load softening test up to a high temperature simulated in the temperature, gas composition and charge loading conditions in the blast furnace and Various examinations were repeated by the test operation using the test blast furnace, and the knowledge shown in the following (a) to (c) was obtained to complete the present invention.

  (A) If the coke reactivity index (CRI) is 30% or more, the CO concentration in the reducing gas is sufficiently increased by the progress of the solution loss reaction, so that the ultimate reduction rate of the ore is increased. Since the reaction rate (mass reduction rate) also increases, the coke strength decreases and coke pulverization proceeds in the blast furnace.

  (B) If the reducibility index (RI) of the sintered ore is 70% or more, the ultimate reduction rate in the blast furnace becomes high, and the FeO concentration in the slag at the time of melt dripping decreases, so coke and FeO The coke deterioration due to the reaction is suppressed, and the coke strength at the lower part of the blast furnace is maintained at a high value.

  (C) If the amount of slag in the blast furnace is 270 kg or less per ton of hot metal, the amount of unburned char derived from the injected pulverized coal is trapped in the slag, and the unburned char is consumed in the gasification reaction Therefore, the amount of coke gasification reaction is reduced by that amount, and the reduction in coke strength at the bottom of the blast furnace is suppressed.

  The present invention has been completed based on the above findings, and the gist of the present invention is the blast furnace operating method described below.

That is, in the operation method of the blast furnace blowing pulverized coal from the "tuyere, the weighted average value of the coke reactivity index of total charge coke (CRI) of 30% or more, and the sintered ore of ZenSoIrisho ore A blast furnace operating method characterized in that the weighted average value of the reducibility index (RI) is 70% or more and the amount of blast furnace slag is 270 kg or less per ton of hot metal.

  In the present invention, “all-charged coke” means all types of coke charged into the blast furnace. For example, coke having different properties such as reactivity index and particle size is mixed or divided and charged. If so, it refers to all those coke.

"Coke reactivity index (CRI)" is the mass reduction rate of coke when coke with a particle size of 19-21 mm is allowed to react for 120 minutes at 1100 ° C with CO ₂ gas flowing at a flow rate of 5 NL / min. The details are as described later.

  “Fully charged sinter” means all types of sinter charged in the blast furnace. For example, sinter with different properties such as reducibility index and particle size is blended or divided. Means all of those sintered ore.

“Sintered ore reducibility index (RI)” means the reducibility index of sintered ore as defined in JIS M 8713, and the sintered ore having a particle diameter of 19 to 21 mm at 900 ° C. CO: 30% and CO _2: 70% of the gas mixture flowing at a flow rate of 15 NL / min, refers to the final reduction rate when allowed to proceed for 180 minutes reduction, details are as described below.

  The “weighted average value” means a weighted average value based on the amount of coke charged (mass or volume) or a weighted average value based on the amount of sintered ore charged (mass or volume).

  According to the method of the present invention, even when highly reactive coke is used, the coke coldness can be reduced by optimizing the coke reactivity, the sinter reducibility, and the blast furnace slag amount. Reduces coke strength deterioration and pulverization in the blast furnace and reduces the amount of reducing material used in the blast furnace with stable air permeability without increasing the cost of pig iron production due to improved strength be able to.

The blast furnace operating method of the present invention will be described in more detail. The present invention, in operation method of the blast furnace blowing pulverized coal from the tuyere, the weighted average value of the coke reactivity index of total charge coke (CRI) of 30% or more, and sintered ore of ZenSoIrisho ore This is a blast furnace operating method in which the weighted average value of the reducibility index (RI) is set to 70% or more and the amount of blast furnace slag is set to 270 kg or less per ton of hot metal.

  As described above, when the coke reactivity is increased, the mass of coke is reduced by the gasification reaction, the coke matrix constituting the particles becomes brittle, the strength of the particles as a structure is reduced, and in the blast furnace It becomes easy to be pulverized by load, impact and friction. As described above, when coke pulverization progresses in the blast furnace, the air permeability in the furnace deteriorates, and there is a possibility that the furnace condition may be deteriorated.

(A) Effect of coke reactivity and sintered ore reducibility on in-furnace reaction We changed coke reactivity index (CRI) and sintered ore reducibility index (RI). In order to investigate how the reaction efficiency of coke and sinter changes in the blast furnace, a high temperature load softening test was conducted.

  FIG. 1 is a view showing a high-temperature load softening test apparatus for a blast furnace charge, wherein FIG. 1 (a) shows a longitudinal sectional view of the testing apparatus, and FIG. 1 (b) shows an enlarged view of a longitudinal section of a sample portion. To express. FIG. 2 is a diagram showing the high temperature load softening test conditions of the blast furnace charge. FIG. 2 (a) shows the temporal change of the sample temperature, and FIG. 2 (b) shows the temporal change of the reducing gas flow rate. FIG. 7C shows the change with time of the load.

  As a blast furnace charge sample 3, a coke sample 31 and an ore sample 32 are alternately charged in a total of four layers in a graphite crucible 2 provided with a large number of through holes for reducing gas flow at the bottom, and these are placed in a vertical electric furnace. 1, the reducing gas 4 is introduced from the lower part of the vertical electric furnace 1, and the load control device 6 passes the reducing gas 4 through the packed bed of the blast furnace charge sample 3 in the graphite crucible 2. A load was applied to the packed bed, and a load softening and reduction test was performed under heating and heating conditions.

Here, the temperature of the sample packed bed measured by the temperature measuring device 7 is controlled by controlling the electric power supplied to the graphite heating element 5 of the vertical electric furnace 1, and the reducing gas composition is determined by the gas flow rate control device 10. The flow rates of CO gas, CO ₂ gas and N ₂ gas were controlled by the above, and the load was changed with time by the load control device 6 under the conditions shown in FIG. Further, the exhaust gas composition after the reducing gas 4 has passed through the sample packed bed is continuously analyzed by the exhaust gas analyzer 12, and the gas pressure loss in the sample packed bed is determined by the pressure of the gas on the inlet side and the outlet side of the sample packed bed. The difference was determined by measuring with the pressure measuring device 8. The molten drop was collected by a turntable 9 provided below the vertical electric furnace 1 and subjected to chemical analysis to obtain a slag composition such as FeO.

  First, the effect of changing the reactivity index (CRI) of coke with the properties of sintered ore fixed was investigated.

  FIG. 3 is a diagram showing the effect of coke reactivity index (CRI) on the ultimate reduction rate of sintered ore, and FIG. 4 is a diagram showing the effect of coke reactivity index (CRI) on the reaction rate of coke. It is.

  According to the results of FIG. 3, when the coke reactivity index (CRI) is increased, the ultimate reduction rate of the sintered ore is improved, and the reduction reaction efficiency of the sintered ore in the blast furnace is improved. In particular, when the coke reactivity index (CRI) is 30% or more, the CO concentration in the reducing gas is sufficiently increased by the progress of the solution loss reaction, so the reduction rate of the sintered ore reaches a high value of about 88% or more. .

  However, since the gasification reaction of coke is promoted at the same time, as can be seen from the results of FIG. 4, the coke substrate is deteriorated due to the increase of the coke reaction rate (mass reduction rate), and the coke strength is increased. Is expected to cause the coke particles to collapse and pulverize. Here, the coke reaction rate is a value calculated by {(pre-reaction coke mass−post-reaction coke mass) / (pre-reaction coke mass)} × 100 (%).

Here, the coke reactivity index (CRI) targeted by the present inventors is different from the JIS reactivity of coke described in Patent Document 1 or Patent Document 2 in the measurement method, and the contents are completely different. It is a different index. That is, the coke reactivity index (CRI) is a mass reduction rate of coke after reacting for 120 minutes by flowing CO ₂ gas at a flow rate of 5 NL / min to 200 g of coke having a particle diameter of 19 to 21 mm at 1100 ° C. Is calculated by the following equation (1).

CRI = {(pre-reaction coke mass−reaction coke mass) / (pre-reaction coke mass)} × 100 (%) (1)
On the other hand, the JIS reactivity of coke is an index for evaluating the reactivity of the substrate of coke as defined in JIS K 2151. It is about 100 g of coke having a particle size of 840 to 1680 μm at a flow rate of 50 mL at 950 ° C. The CO ₂ gas is allowed to react and the reactivity is obtained based on the exhaust gas composition after the reaction. The exhaust gas composition is measured at least twice or more from 20 minutes to 60 minutes after the start of the reaction to obtain an average value, and the reactivity is calculated using the following equation (2).

JIS reactivity = {CO / (CO + CO ₂ )} × 100 (%) (2)
Here, CO represents the concentration (%) of CO gas generated by the reaction, and CO ₂ represents the concentration (%) of unreacted CO ₂ gas (that is, CO ₂ = 100−CO).

  As described above, in the present invention, the coke reactivity index (CRI) used is an index indicating the reactivity of the coke coke approximated to the coke reaction conditions in the blast furnace, and is a JIS for evaluating the reactivity of the coke substrate. Reactivity is a fundamentally different index.

  Next, the effect of the coke on the post-reaction strength when the sinter reducibility index (RI) was changed was investigated with the properties of the coke sample being constant.

  FIG. 5 is a diagram showing the influence of the reducibility index (RI) of sintered ore on the strength of coke after reaction. Here, a coke sample having a coke reactivity index (CRI) of 30.5% was used. According to the results shown in the figure, as the reducibility index (RI) of the sintered ore increases, the post-reaction strength (I (600, +9.5)) of the coke increases. This is because when the sinter reducibility index (RI) is improved, the ultimate reduction ratio at the time of melting and dropping of the sinter is increased, the FeO concentration in the dropping slag is lowered, and coke and molten FeO. This is because deterioration due to the reaction of coke was suppressed because the amount of reaction with was reduced. In addition, it is understood from the results in the figure that when the sinter reducibility index (RI) is 70% or more, the coke strength at the lower part of the blast furnace is maintained at a high level.

  Here, the sintered ore reducibility index (RI) and the strength after coke reaction (I (600, +9.5)) will be described.

As described above, the sinter ore reducibility index (RI) means the reducibility index of the sinter specified in JIS M 8713. Te, CO: 30% and CO _2: 70% of the gas mixture flowing at a flow rate of 15 NL / min, to perform the 180 minutes reduction, the final reduction rate and the mass change of the sample after the reduction, the following (3 ).

RI = {(WO-WF) / W1 * (0.430A-0.112B)} * 100 (%)
... (3)
Here, W1 is the measured sample mass (g), WO is the sample mass (g) just before the start of reduction, WF is the sample mass (g) at the end of reduction, and A is the total iron content in the sample before reduction. And B represents the content (%) of ferrous oxide in the pre-reduction sample, respectively.

  Further, the post-reaction strength (I (600, +9.5)) of the coke is 140 mm in diameter and 140 mm in length from 140 to 150 g of coke having a particle diameter of 15 to 20 mm collected from the load softening test or from the inside of the test blast furnace described later. A cylindrical metal drum (hereinafter also referred to as “I-type drum”) with both ends of 700 mm is charged, and passes through the center in the longitudinal direction of the drum at 20 rpm around an axis perpendicular to the cylinder central axis. The mass fraction of particles having a particle size of 9.5 mm or more in the coke sample after a total of 600 revolutions for 30 minutes is expressed as a percentage (%). The strength of the coke after reaction (I (600, +9.5)) is hereinafter also referred to as “strength after coke reaction (I)”.

  As a method of suppressing coke pulverization when using highly reactive coke, Patent Document 3 discloses an operation method in which the coke reactivity is changed according to the amount of pulverized coal blown from the tuyere. ing. This method focuses on pulverization of the coke raceway, and when the amount of pulverized coal increases, the oxygen concentration in the raceway decreases, so the deteriorated layer on the coke surface is not consumed. It is intended to prevent pulverization. That is, when the amount of pulverized coal increases, the reactivity of coke is improved, and before the coke reaches the raceway, the deteriorated layer on the surface of the coke particles disappears by the gasification reaction, and the coke powder in the raceway It is a method of suppressing the conversion.

  On the other hand, Non-Patent Document 1 reports coke deterioration behavior when pulverized coal is different from the above. That is, the unburned char blown out of the raceway area without being burned in the raceway has a high specific surface area and high reactivity, so the coke descends in the furnace and reaches the raceway. This unburned char is preferentially consumed in the gasification reaction, and therefore, deterioration due to coke reaction is unlikely to occur.

(B) Effect of Blast Furnace Slag Amount on Decrease in Coke Strength Accordingly, the present inventors further examined a method for suppressing deterioration due to coke reaction to the maximum by paying attention to the behavior of unburned char. In other words, in order to suppress deterioration due to the reaction of coke, it is necessary to consume unburned char preferentially by the gasification reaction prior to coke. To that end, unburned char is a factor other than the gasification reaction. From the viewpoint that it is necessary to prevent it from disappearing due to heat, we focused on metal and slag that melted and dropped in large quantities in the lower part of the furnace.

  If the above-mentioned unburned char is trapped by a large amount of dripping metal and slag and consumed for carburizing, the unburned char consumed for the gasification reaction is reduced, and therefore the coke gasification reaction in the lower part of the furnace is suppressed. However, it is difficult to suppress the strength deterioration. If the amount of metal and the amount of slag can be reduced, unburned char is consumed in the gasification reaction in preference to coke, and deterioration due to the reaction of coke can be suppressed. Since the amount of metal is determined by the planned pig iron production, it is difficult to reduce the amount, but the amount of slag can be adjusted and reduced by raw material quality design.

Therefore, a test operation was carried out by changing the amount of slag using a test blast furnace, and the change in strength after reaction of coke in the furnace was investigated. FIG. 6 is a diagram schematically showing a longitudinal section of the test blast furnace used for the test operation. The test blast furnace has a hearth diameter (b in the figure) of 0.9 m, a height from the tuyere to the stock level (a in the figure) of 4.5 m, and a furnace internal volume of 3.6 m ³ . Three tuyere 101 are installed on the side wall of the furnace body at a height of 0.8 m from the bottom of the furnace with different orientations by 120 degrees in the circumferential direction. One outlet 102 is provided in the bottom wall of the furnace, and a coke charging hopper 103, an ore charging hopper 104, and an in-furnace gas discharge port 105 are installed in the upper part of the furnace. Further, a coke sampler 107 was installed 300 mm above the tuyere level, and coke was collected during operation to investigate properties such as strength.

  FIG. 7 is a diagram showing the influence of the amount of blast furnace slag on the strength of coke collected from the lower part of the furnace using a coke sampler of the test blast furnace. According to the results shown in the figure, the coke strength index (I) can be increased by reducing the amount of blast furnace slag. In particular, if the amount of slag in the blast furnace is 270 kg per ton of hot metal (hereinafter also referred to as “270 kg / t-hot metal” or “270 kg / t”), unburned char derived from the injected pulverized coal is contained in the slag. The amount of trapped carbon dioxide is reduced, the unburned char is consumed in the gasification reaction, the amount of coke gasification reaction is reduced, and the decrease in coke strength at the bottom of the blast furnace is suppressed, resulting in a high value of coke strength. Can be maintained.

(C) Appropriate range of properties of coke and sintered ore and amount of blast furnace slag Hereinafter, the reason for limiting the present invention to the above range and a preferable range will be described.

The weighted average value of 1) total charge coke reactivity index (CRI) of 30% or more:
As described above, when the coke reactivity index (CRI) is 30% or more, the CO concentration in the reducing gas is sufficiently increased by the progress of the solution loss reaction, and high reduction efficiency of the sintered ore in the furnace is obtained. Therefore, the appropriate range of CRI is set to 30% or more. In addition, when coke having different properties such as a coke reactivity index is blended or divided and charged, a value obtained by weighted average of the CRI of all types of coke may be used. In addition, the preferable range of CRI is 33% or more.

2) the reducible index ZenSoIrisho ore weighted average of (RI) is less than 70%:
If the reducibility index (RI) of the sintered ore is 70% or more, the ultimate reduction rate in the blast furnace becomes high, the FeO concentration in the slag at the time of dropping of the sintered ore decreases, and coke and molten FeO The coke strength based on the reaction with the coke was suppressed, and the coke strength at the lower part of the furnace was maintained at a high value, so the appropriate range of RI was set to 70% or more. Here, when the sintered ore having different RI values are mixed or divided and charged, a value obtained by weighted averaging the RIs of all types of sintered ores according to the charged amount is used. Note that the preferable range of RI is 71% or more.

3) blast furnace slag amounts to 270 (kg / t-hot metal) below:
If the amount of slag in the blast furnace is 270 kg / t-molten metal or less, the amount of unburned char derived from the injected pulverized coal is trapped in the slag and consumed in the gasification reaction. A reduction in coke strength due to the gasification reaction is suppressed. Therefore, the slag amount of the blast furnace was set to 270 (kg / t-molten metal) or less. In addition, the range of preferable slag amount is 260 (kg / t-molten metal) or less.

  Blast furnace operation that suppresses coke deterioration and ensures air permeability in the blast furnace and reduces the amount of reducing material used by adjusting the operation specifications so as to satisfy all the appropriate ranges of 1) to 3) described above. Is achieved.

  In order to confirm the effect of the blast furnace operation method of the present invention, the test operation was performed using the test blast furnace described above, and the results were evaluated.

  Table 1 shows the main component composition of the charge used in the test operation, and Table 2 shows the results of the charge amount, the pulverized coal injection amount, and the slag amount.

  In the test blast furnace, the heat loss per molten iron unit mass (1 ton) is larger than that in the actual blast furnace, so that the reducing material ratio is higher than that in the actual blast furnace. Therefore, the amount of slag generated from the reducing material is small. Become more. Therefore, in the test operation, in order to reduce the amount of slag to a value equivalent to that of an actual blast furnace, ordinary coke and low-ash oil coke were blended by 50% by mass, respectively.

  Table 3 shows the reactivity index (CRI) of the charged coke and the reducibility index (RI) of the sintered ore, the amount of slag, the ratio of the reducing material as the test result, the strength of the coke collected in the furnace (I ) Respectively.

  In Table 3, the reducing material ratio represents the sum of the coke ratio and the pulverized coal ratio, and the coke strength (I) is the coke sampled from the lower part of the furnace during the test operation by the coke sampler installed in the test blast furnace. After cooling, the product is visually separated into normal coke and oil coke, and the value of post-reaction strength (I (600, +9.5)) measured with the above-mentioned type I drum for normal coke is shown.

  The evaluation of test results was classified as follows. That is, for the reducing material ratio, the case of less than 700 kg / t is good (◯), the case of 700 kg / t or more is bad (x), and the coke strength (I) is good when it is 84.5% or more. (○), the case of less than 84.5% was regarded as defective (x). And when both were favorable, comprehensive evaluation was set to favorable ((circle)), and when at least one of said was unsatisfactory, comprehensive evaluation was set to defect (x).

  Test Nos. 1 and 2 are tests on examples of the present invention that satisfy all the ranges of coke CRI, sintered ore RI, and blast furnace slag specified in the present invention, and test Nos. 3 to 7 are coke CRI, sintered At least one of the ore RI and the amount of blast furnace slag is a comparative example outside the range defined in the present invention.

  In Test Nos. 1 and 2 of the examples of the present invention, the reducing material ratio was low, and the coke strength (I) was maintained at a high level. That is, a high reduction efficiency of the sintered ore in the furnace was achieved, and the air permeability in the furnace was maintained well, and the overall evaluation was good.

  On the other hand, in the test number 3 of the comparative example, since the coke CRI and the sintered ore RI were both within the range defined in the present invention, the reducing material ratio was low and good, but the slag amount was Since it was high, the reaction amount of coke increased, the coke strength (I) decreased, the air permeability in the furnace was also inhibited, and the overall evaluation was poor. Moreover, since test number 4 of the comparative example had a low sintered ore RI and a large amount of slag, the reducing material ratio was high, the coke strength (I) was also lowered, and the overall evaluation was poor.

  In the test number 5 of the comparative example, the sintered ore RI and the slag amount satisfied the ranges specified in the present invention, but the coke strength (I) was maintained high because the coke CRI was low, but The reduction efficiency of the ore was low, the ratio of reducing materials increased, and the overall evaluation was poor. In the test number 6 of the comparative example, the sintered ore RI was within the range specified in the present invention, but the coke strength (I) was maintained high because the coke CRI was low and the amount of slag was high. The reduction efficiency of sintered ore was low, the ratio of reducing materials increased, and the overall evaluation was poor. And in the test number 7 of a comparative example, since all of coke CRI, sintered ore RI, and the amount of slag were outside the range prescribed | regulated by this invention, the reduction | restoration efficiency of sintered ore is very low, Therefore, reducing material ratio Became extremely high and the overall evaluation was poor.

  According to the method of the present invention, even when highly reactive coke is used, by adjusting the coke reactivity, the sinter reducibility, and the blast furnace slag amount to an appropriate range, Reduces coke strength deterioration and pulverization in the blast furnace and reduces the amount of reducing material used in the blast furnace with stable air permeability without increasing the cost of pig iron production by improving cold strength Can be achieved. Therefore, the blast furnace operating method of the present invention can be widely applied in the blast furnace operating field where both good in-furnace air permeability and reduction of the reducing material ratio are required.

It is a figure which shows the high temperature load softening test apparatus of a blast furnace charge, The figure (a) represents the longitudinal cross-sectional view of a test apparatus, and the figure (b) represents the enlarged view of the longitudinal cross-section of a sample part. It is a figure which shows the high temperature load softening test condition of a blast furnace charge, the figure (a) is a time change of sample temperature, the figure (b) is a time change of a reducing gas flow rate, and the figure (c) ) Represents the change in load over time. It is a figure which shows the influence of the coke reactivity index (CRI) on the ultimate reduction rate of a sintered ore. It is a figure which shows the influence of the coke reactivity index (CRI) on the reaction rate of coke. It is a figure which shows the influence of the sintered ore reducibility index (RI) on the strength after reaction of coke. It is a figure which shows typically the longitudinal cross-section of a test blast furnace. It is a figure which shows the influence of the amount of blast furnace slag on the intensity | strength of the coke extract | collected from the furnace lower part.

Explanation of symbols

1: vertical electric furnace, 2: graphite crucible, 3: blast furnace charge sample, 31: coke sample,
32: Sintered ore sample, 4: Reducing gas, 5: Graphite heating element, 6: Load control device,
7: temperature measuring device, 8: gas pressure measuring device, 9: turntable, 10: gas flow rate control device, 11: exhaust gas, 12: exhaust gas analyzer, 101: tuyere,
102: Outlet, 103: Coke charging hopper, 104: Ore charging hopper,
105: In-furnace gas discharge port, 106: Insulating material and refractory, 107: Coke sampler.

Claims (1)

In operation method for a blast furnace blowing pulverized coal from the tuyere, a weighted average value was 30% or more, and sintered ore reducibility index ZenSoIrisho ore coke reactivity index of total charge coke (CRI) A method of operating a blast furnace, characterized in that a weighted average value of (RI) is 70% or more and a blast furnace slag amount is 270 kg or less per ton of hot metal.

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