JP2015183233A - High furnace operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high furnace operation method capable of improving productivity and reducing discharged COeven under an operation condition with a dust coal ratio of 150 kg/t-p or more.SOLUTION: When at least two or more of 3 conditions, 60% or less of dust coal weight percentage of particle diameter of 74 μm or less, 25 mass% or less of average volatile content of the dust coal, and 1100°C or less of a blast temperature, are satisfied with strength of coke injected from a furnace top of DI[%] of 87 or less, dust coal, a combustion supporting gas, and a combustible gas are blown from one lance, and dust coal and a combustible gas are blown from the other lance by using two lances per a tuyere. In this case, concentrations of the combustion supporting gas and the combustible gas in the one lance are set at 50 to 70 vol% and 10 to 30 vol%, concentration of the combustible gas in the other lance is set at 60 to 97 vol%, and concentrations of the combustion supporting gas and the combustible gas in the lances are set larger as strength of coke reduces.

Description

The present invention relates to a method of operating a blast furnace that aims to improve productivity and reduce exhaust CO ₂ by blowing pulverized coal from a blast furnace tuyere and raising the combustion temperature.

In recent years, global warming due to an increase in carbon dioxide emission has become a problem, and the suppression of exhausted CO ₂ is an important issue even in the steel industry. The blast furnace uses coke mainly charged from the top of the furnace and pulverized coal blown from the tuyere as a reducing material, and uses pulverized coal as much as possible from coke due to the difference in carbon dioxide emissions generated by pretreatment. it leads to the suppression of emissions of CO ₂ as a whole. The amount of pulverized coal used per 1 ton of pig iron (injected from the tuyere) is referred to as the pulverized coal ratio (kg / t-pig iron or kg / tp). When the combustion efficiency of pulverized coal is reduced when the volatile content of pulverized coal is 25 mass% or less, the pulverized coal and oxygen are injected into the lance that blows the pulverized coal from the tuyere into the furnace. It is said that combustion efficiency can be improved by supplying the oxygen concentration in the lance to 70 vol% or more. Further, in Patent Document 1, when the lance is a single pipe, a mixture of oxygen and pulverized coal is blown from the lance, and when the lance is a double pipe, fine powder is injected from the inner pipe of the double pipe lance. It has also been proposed to blow charcoal and blow oxygen from between the inner and outer tubes of the double tube lance. Moreover, in the following patent document 2, when the combustion efficiency decreases when the pulverized coal ratio is 150 kg / tp or more during the production reduction operation with a yield ratio of 1.8 or less, pulverized coal with a volatile content of 28 mass% or more is used. While being used, the heat flow ratio represented by the ratio between the solid heat capacity and the gas heat capacity is controlled to 0.8 or less to maintain efficient combustion of pulverized coal.

Japanese Patent No. 4074467 JP 2011-127176 A

The role of pulverized coal in the blast furnace is basically a heat source and a reducing material source, and the combustibility is related to the amount of unburned powder (unburned char) generated (the amount of powder charged into the blast furnace). In the blast furnace, a solution loss reaction represented by C + CO ₂ = 2CO occurs, and the reaction amount varies depending on the operation, but is about 80 to 100 kg-C / tp. As the C source consumed in this reaction, lump coke charged in the blast furnace, small lump coke mixed in the ore, and pulverized coal unburned powder can be considered. ) It is said that pulverized coal unburned powder is consumed preferentially from the difference. In other words, when the flammability of pulverized coal decreases, the amount of unburned powder charged into the blast furnace increases, and as a result of being consumed preferentially by the solution loss reaction, the powder coke that would normally be consumed cannot be consumed. In the furnace. It is thought that when the retained powder coke in the furnace is increased, the porosity and the average particle diameter are decreased, and as a result, the air permeability of the blast furnace is deteriorated. On the other hand, the amount of coke in-furnace generated powder is greatly influenced by the cold strength of the coke (drum strength described in the JIS K 2151 coke test method). Therefore, in terms of evaluating the air permeability of the blast furnace, It is considered important to adjust not only the combustibility of pulverized coal but also the properties of coke.

  In the above-mentioned patent document 1, the pulverized coal has a volatile matter content of 25 mass% or less and a pulverized coal ratio of 150 kg / tp or more. It is a technique that can improve combustion efficiency by supplying charcoal and oxygen and setting the oxygen concentration in the lance to 70 vol% or more, thereby improving the air permeability in the furnace. However, regarding the combustion efficiency, even if it is pulverized coal having the same volatile content of 25 mass% or less, depending on the particle size or the blowing temperature, even if the oxygen concentration in the lance is set to 70 vol% or more, the combustion efficiency does not increase or vice versa. In addition, it has been found that the combustion efficiency may be maintained even if the oxygen concentration in the lance is not set to 70 vol% or more. Further, regarding the air permeability in the furnace, it has been found that even if the combustion efficiency of pulverized coal is somewhat reduced, if the strength of the coke is large, the influence on the air permeability in the furnace may be small. Therefore, although Patent Document 1 is an excellent technique, the effect cannot be exhibited depending on the properties of pulverized coal and coke, and the blowing conditions, or conversely, the effect is excessive, so high pressure oxygen is prepared in the lance. Considering the cost, it can be assumed that it leads to loss.

Further, since further reduction of exhausted CO ₂ is required, for example, it is desired to set the pulverized coal ratio to 170 kg / tp or more, but the high pulverized coal ratio is 170 kg / tp or more. In the charcoal ratio, as described in Patent Document 1, even if pulverized coal is simply blown from the inner pipe of the double pipe lance and oxygen is blown from between the inner pipe and the outer pipe, the combustion temperature is saturated. The combustion efficiency does not increase. In addition, since a large amount of hot air of 1000 to 1200 ° C. is blown into the tuyere, for example, the blowing lance inserted into the tuyere may be exposed to high temperatures, as described in Patent Document 1 described above. In addition, it is impractical to supply a single pipe lance with a mixture of high-concentration oxygen and pulverized coal from the viewpoint of safety.

  Moreover, in the said patent document 2, while a combustion efficiency falls as a pulverized coal ratio 150 kg / tp or more at the time of the production reduction operation of the output ratio 1.8 or less, while using pulverized coal whose volatile matter is 28 mass% or more, The heat flow ratio represented by the ratio between the solid heat capacity and the gas heat capacity is controlled to 0.8 or less to maintain efficient combustion of pulverized coal. However, in order to reduce the heat flow ratio, oxygen enrichment is set to 2.0 or less, preferably 1.5%, which lowers the combustion efficiency of pulverized coal. Depending on the charcoal properties (particle size), even if the volatile content is set to 28 mass% or more, it may be assumed that the effect of improving the combustion efficiency is insufficient.

The present invention has been made paying attention to the above problems, and even if the pulverized coal ratio is an operation condition of 150 kg / tp or more, it is produced by increasing the combustion temperature of the pulverized coal. An object of the present invention is to provide a blast furnace operating method that can improve the performance and reduce the exhausted CO ₂ .

In order to solve the above-mentioned problems, the blast furnace operating method of the present invention is a blast furnace operating method in which pulverized coal with an injection amount of 150 kg / tp or more per 1 ton of pig iron is blown by a lance from a blower tuyere. When the strength of the coke to be added is DI ¹⁵⁰ ₁₅ [%] 87 or less according to the test method described in JISK2151, the weight ratio of pulverized coal having a particle size of 74 μm or less is 60% or less, and the average volatile content of the pulverized coal is When at least two of the three conditions of 25 mass% or less and the blowing temperature of 1100 ° C. or less are satisfied, two lances are used per tuyere, and flammable gas and facile gas from one lance together with pulverized coal. A flammable gas is blown, and a flammable gas is blown together with pulverized coal from the other lance.

The combustion-supporting gas of the present invention is defined as a gas having an oxygen concentration of at least 50 vol% or more.
In addition, the flammable gas used in the present invention is literally a gas that is more flammable than pulverized coal. For example, in addition to hydrogen containing hydrogen as a main component, city gas, LNG, propane gas, in steelworks The generated converter gas, blast furnace gas, coke oven gas, etc. are applicable. Also, shale gas can be used as equivalent to LNG. Shale gas is a natural gas extracted from the shale layer, and is produced from a place other than the conventional gas field, so it is called an unconventional natural gas resource. Combustible gases such as city gas ignite and burn very quickly, and those with a high hydrogen content have high combustion calories, and unlike pulverized coal, flammable gas does not contain ash. It is advantageous for air permeability and heat balance.

The lower limit of the average volatile content of pulverized coal is 5 mass%. If the average volatile content of pulverized coal is less than 5 mass%, the coal is hard and difficult to grind. The lower limit of coke strength is set to 78 in DI ¹⁵⁰ ₁₅ [%]. If the coke strength is less than DI ¹⁵⁰ ₁₅ [%] 78, the coal is not sufficiently shrunk, so the coke becomes undried and damages the coke oven. The lower limit of the weight ratio of pulverized coal having a particle size of 74 μm or less is 30%. When the weight ratio of the pulverized coal having a particle size of 74 μm or less is less than 30%, the temperature rise of the pulverized coal is slow and does not ignite, so that the combustibility is rapidly lowered. Further, the lower limit value of the blowing temperature is set to 900 ° C. Since the bricks of the hot stove are designed to mesh at 900 to 1200 ° C, if the air temperature is less than 900 ° C, the bricks of the hot stove are worn. The upper limit of the amount of pulverized coal injected per 1 ton of pig iron is 250 kg / tp. When the amount of pulverized coal injection per 1 ton of pig iron exceeds 250 kg / tp, the coke replacement rate decreases due to a significant decrease in combustibility, and the tuyere temperature (theoretical combustion temperature) is maintained in terms of operation. Therefore, it is not desirable because it is difficult to adjust the equipment capacity such as greatly increasing the oxygen concentration and the blowing temperature, or drastically reducing the blowing humidity.

  Further, the concentration of the combustion-supporting gas and the concentration of the flammable gas that are blown together with the pulverized coal from the one lance are 50 to 70 vol%, respectively, as the concentration in the gas conveyed by the one lance. It is 10-30 vol%, The density | concentration of the combustible gas injected with the said pulverized coal from said other lance is 60-97 vol% as a density | concentration in the gas conveyed by said other lance, It is characterized by the above-mentioned. To do.

When the strength of the coke is DI ¹⁵⁰ ₁₅ [%] 85 or less, the concentration of the combustion-supporting gas and the flammable gas that are blown together with the pulverized coal from the one lance are the one lance. Concentrations of the flammable gas that is blown together with the pulverized coal from the other lance are 50-80 vol% and 10-40 vol%, respectively, as the concentrations in the gas conveyed in It is characterized by being 70-97 vol% as a density | concentration in the gas to be performed.

Further, when the strength of the coke is DI ¹⁵⁰ ₁₅ [%] 83 or less, the concentration of the combustion-supporting gas and the flammable gas that are blown together with the pulverized coal from the one lance are the one lance. Concentrations of the flammable gas blown from the other lance together with the pulverized coal are 50 to 90 vol% and 10 to 50 vol%, respectively. It is characterized by being 80 to 97 vol% as a concentration in the gas to be produced.

  In addition, in order to aim at the stable operation of a blast furnace according to the conditions where the combustion efficiency of pulverized coal falls, the injection amount of the combustion-supporting gas and flammable gas in the present invention will be described later. As a result of gradually increasing the amount of flammable gas blown and reducing the carrier gas for conveying pulverized coal accordingly.

Thus, according to the blast furnace operating method of the present invention, while considering the various conditions under which the combustion efficiency of pulverized coal decreases together with the coke strength, comprehensively considering the air permeability state of the blast furnace, By improving the combustion efficiency of pulverized coal, it is possible to efficiently improve productivity and reduce exhaust CO ₂ . In other words, the combustion efficiency of the pulverized coal is judged from the amount of pulverized coal blown from the tuyere, the properties of the pulverized coal (particle size, volatile content), and the blowing temperature, and the breathability is determined from the combustion efficiency of the pulverized coal and the strength of the coke used. By comprehensively judging, the combustion efficiency of pulverized coal can be set efficiently within the optimum range. As a result, it is possible to maintain and improve the combustion efficiency of pulverized coal, which in turn stabilizes the air permeability of the blast furnace, and as a result, it is possible to efficiently improve productivity and reduce exhaust CO _2. It is.

It is a longitudinal cross-sectional view which shows one Embodiment of the blast furnace to which the blast furnace operating method of this invention was applied.

Next, an embodiment of the blast furnace operating method of the present invention will be described with reference to the drawings.
FIG. 1 is an overall view of a blast furnace to which the blast furnace operating method of the present embodiment is applied. As shown in the figure, a blast pipe 2 for blowing hot air is connected to the tuyere 3 of the blast furnace 1, and a lance 4 is installed through the blast pipe 2. A combustion space called a raceway 5 exists in the coke deposit layer in the hot air blowing direction ahead of the tuyere 3, and iron ore is reduced, that is, ironmaking is mainly performed in this combustion space. In the figure, only one lance 4 is inserted into the left blower pipe 2 shown in the figure, but as is well known, either the blower pipe 2 or the tuyere 3 arranged circumferentially along the furnace wall. It is also possible to insert and set the lance 4. Further, the number of lances per tuyere is not limited to one, and two or more lances can be inserted. Moreover, the form of a lance can be applied to a single pipe lance, a double pipe lance, or a bundle of a plurality of lances.

As is well known, the pulverized coal that has passed through the tuyere 3 from the lance 4 and is blown into the raceway 5 is coke and its volatile matter and fixed carbon are burned, and remains unburned. The aggregate of carbon and ash called is discharged from the raceway as unburned char (unburned powder). Since char is mainly fixed carbon, a reaction called a carbon dissolution reaction occurs along with a combustion reaction. Moreover, when the volatile matter of the pulverized coal blown into the blower pipe 2 from the lance 4 is high, the ignition of the pulverized coal is promoted due to the increase in the volatile matter, and the temperature rise of the pulverized coal due to the increase in the combustion amount of the volatile matter. The rate and maximum temperature increase, and the char reaction rate increases due to the dispersibility of pulverized coal and the increase in temperature. At this time, it is considered that the pulverized coal is dispersed with the vaporization expansion of the volatile matter, the volatile matter is combusted, and the pulverized coal is rapidly heated and heated by this combustion heat. Charcoal burns. Regarding the coke strength DI ¹⁵⁰ ₁₅ [%] defined in JISK2151, the larger the coke strength DI ¹⁵⁰ ₁₅ [%], the smaller the proportion of coke powder in the furnace. For example, the amount of coke powder deposited on the furnace core is smaller. It will be smaller.

Next, in a blast furnace with a furnace volume of 5000 m ³ , the above-mentioned coke strength DI ¹⁵⁰ ₁₅ [%], pulverized coal amount, pulverized coal properties (particle size, volatile content), operation temperature to evaluate the air permeability by changing the blowing temperature Went. The amount of air flow was controlled so that the amount of brewing was constant at 10000 t / day (sometimes expressed as d), and the air permeability at that time was compared for each condition. As is well known, the air permeability is obtained from the pressure difference between the pressure at the top of the furnace and the blowing pressure and the blowing amount. During this test operation period, the blast moisture was adjusted so that the tuyere tip temperature was in a certain range, and the hot metal temperature was within a range of 1500 ° C. ± 10 ° C. at each level. As shown in Table 1 below, as a base condition 1, a coke ratio of 340 kg / tp (-p is omitted in the figure), a pulverized coal ratio of 150 kg / tp, an air blowing temperature of 1100 ° C., a coke strength DI ¹⁵⁰ ₁₅ [% ] 87, Operation with pulverized coal volatile matter 25 mass%, particle size of 74 μm or less pulverized coal particle size 60 mass%, the air permeability at that time was set to 1.0, and the air permeability when operating conditions were changed to the following relative comparison did. The larger the numerical value, the worse the air permeability. However, until the air permeability was about 1.05, it was an acceptable range for stable operation. In the base conditions, one single tube lance was used per tuyere.

  As a result of operating the air temperature, the pulverized coal volatile content, and the pulverized coal particle size in the direction of improving the combustion efficiency, the base 2 improved both the coke ratio and the air permeability as expected. The direction in which the combustion efficiency is improved is that the blast temperature is increased, the pulverized coal volatiles are increased, and the pulverized coal particle size is increased (because the weight percent of the pulverized coal particles having a particle size of 74 μm or less is the pulverized coal particle size). ) Means. In Base 3, as compared with Base 1, only the pulverized coal ratio was +10 kg / tp. As a result, the air permeability was slightly deteriorated, but it was within the allowable range for stable operation. In the bases 4 to 6, the pulverized coal volatile matter, the pulverized coal particle size, and the air blowing temperature were each operated with respect to the base 3 in the direction in which the combustion efficiency was decreased. The direction in which the combustion efficiency decreases means that the blast temperature is decreased, the pulverized coal volatile content is decreased, and the pulverized coal particle size is decreased. As a result, in Bases 4 to 6, although the air permeability was somewhat deteriorated, it was within the allowable range for stable operation.

In the bases 7 to 9, the combustion efficiency is lowered by combining two items of the pulverized coal volatile matter, the pulverized coal particle size, and the blowing temperature with respect to the base 3 under the condition of coke strength DI ¹⁵⁰ ₁₅ [%] 88. Operated. As a result, in the bases 7 to 9, the air permeability was slightly deteriorated, but was within the allowable range for stable operation. This is considered to be an effect of improving the coke strength DI ¹⁵⁰ ₁₅ [%]. That is, since the coke strength DI ¹⁵⁰ ₁₅ [%] was improved, the accumulation of the powder coke in the furnace was suppressed, and it is considered that the air permeability was not significantly impaired. In the bases 10 to 12, the coke strength DI ¹⁵⁰ ₁₅ [%] is reduced to 85.5 compared to the base 3, and further, combustion efficiency is obtained by combining two items of pulverized coal volatile matter, pulverized coal particle size, and blowing temperature. Was operated in the direction of decreasing. As a result, the air permeability was greatly deteriorated and the coke ratio was increased, but stable operation was difficult. As described above, this is considered to be because the coke strength DI ¹⁵⁰ ₁₅ [%] was reduced and the in-furnace deposition of the fine coke deteriorated.

  The base 13 has one to two pulverized coal blowing lances with respect to the base 12. By using two lances, the dispersibility of the pulverized coal is improved, and the contact efficiency with hot air is improved. As a result, the combustibility is improved, so that the air permeability is improved with respect to the base 12. However, compared with the base 1, the air permeability is inferior and the operation cannot be stabilized. In the base 14, one of the two lances is blown with pulverized coal, and the remaining one is blown with city gas as a flammable gas. By blowing city gas from one of the two lances, the temperature of the pulverized coal particles is increased by rapid combustion of the city gas, and the flammability of the pulverized coal is improved. And breathability is improved. However, compared with the base 1, the air permeability is still inferior and the operation is not stable.

  In all of the following case conditions, two lances were used per tuyere, a triple pipe lance was used for one lance, and a double pipe lance was used for the other lance. Of these, the triple lance, which is one of the lances, blows pulverized coal from the inner pipe of the triple pipe lance, blows oxygen as a combustion-supporting gas between the inner pipe and the intermediate pipe, City gas was injected as a flammable gas. At that time, the pulverized coal is conveyed from the inner pipe of the triple pipe lance together with a carrier gas such as nitrogen. On the other hand, in the double pipe lance which is the other lance, pulverized coal was blown from the inner pipe of the double pipe lance, and city gas was blown as a flammable gas between the inner pipe and the outer pipe. Here too, the pulverized coal is transported from the inner tube of the double tube lance together with a carrier gas such as nitrogen. Hereinafter, a triple pipe lance which is one lance is also referred to as a first lance, and a double pipe lance which is the other lance is also referred to as a second lance. The lance oxygen concentration of the first lance in the table is the oxygen concentration in the gas carried by the triple pipe lance, and the lance city gas concentration of the first lance is the city gas concentration in the gas carried by the triple pipe lance. vol%. Similarly, the lance city gas concentration of the second lance in the table is the city gas concentration in the gas conveyed by the double pipe lance, and its unit is vol%.

  The above-mentioned blowing pattern in the triple pipe lance is an example, and each of pulverized coal, oxygen, and city gas is blown from any position between the inner pipe, the inner pipe and the intermediate pipe, and between the intermediate pipe and the outer pipe. The blowing pattern in the double pipe lance may be the reverse of the above. Further, instead of the triple pipe lance, a lance in which two or more single pipes are bundled or a double pipe lance may be used. In that case, for example, pulverized coal is blown from one of the three bundled single pipes. The flammable gas may be blown from any one and the oxygen may be blown from any. Also, flammable gas and pulverized coal are mixed in advance and blown from one of the two single pipes bundled, or from the inner pipe of the double pipe lance or between the inner pipe and the outer pipe. It may be. In any case, it is desirable to blow oxygen or city gas in the immediate vicinity of the pulverized coal to be blown. Further, instead of the double pipe lance, a lance in which two single pipes are bundled may be used. In that case, pulverized coal is blown from either one of the two bundled single pipes, and from either one of the two pipes. A flammable gas may be blown.

  Case 1 applies the blast furnace operating method of the present embodiment in which oxygen and city gas are blown together with pulverized coal from the lance to the conditions of the base 10. That is, pulverized coal is blown together with carrier gas from the inner pipe of the triple pipe lance (first lance), which is one of the lances, oxygen is blown from between the inner pipe and the intermediate pipe, and the city is inserted from between the intermediate pipe and the outer pipe. While blowing gas, pulverized coal was blown together with carrier gas from the inner pipe of the other lance, a double pipe lance (second lance), and city gas was blown from between the inner pipe and the outer pipe. However, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance), that is, the lance that blows in oxygen, city gas and pulverized coal is 45 vol%, and is also conveyed by the triple pipe lance (first lance). The lance city gas concentration in the gas is 8 vol%, and the lance city gas concentration in the gas conveyed by the double pipe lance (second lance), that is, the lance that blows in city gas and pulverized coal, is only 50 vol%. The air permeability improvement effect was insufficient.

  In contrast, Cases 2 to 4 have a lance oxygen concentration of 55 vol% in the gas conveyed by the triple pipe lance (first lance) with respect to the bases 10 to 12, respectively, and a triple pipe lance (first lance). The concentration of the lance city gas in the gas transported by the lance is 12 vol%, and the concentration of the lance city gas in the gas transported by the double pipe lance (second lance) is 65 vol%. As a result, stable operation became possible. In addition, in cases 5 to 7, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 65 vol% and the triple pipe lance (first lance) conveys the bases 10 to 12, respectively. The lance city gas concentration in the gas to be transferred is 18 vol%, and the lance city gas concentration in the gas conveyed by the double pipe lance (second lance) is 75 vol%. Compared to cases 2 to 4, A further air permeability improvement effect was confirmed, and the air permeability was improved even when compared with the base 1 condition. Furthermore, in the case 8, the pulverized coal is blown together with the carrier gas from the inner pipe of the triple pipe lance (first lance), which is one of the lances, under the same conditions as the cases 2 to 4 with respect to the base 1 condition. Oxygen is blown from between the pipe and the intermediate pipe, city gas is blown from between the intermediate pipe and the outer pipe, and pulverized coal together with the carrier gas from the inner pipe of the other lance, the double pipe lance (second lance). And the blast furnace operating method of this embodiment in which city gas is blown from between the inner pipe and the outer pipe is applied. As is apparent from the table, the pulverized coal ratio can be increased by the effect of improving the combustion efficiency of the pulverized coal, and the coke ratio can be significantly reduced under good air permeability conditions.

In cases 9 to 11, the coke strength DI ¹⁵⁰ ₁₅ [%] was reduced from 85.5 to 84.5 as compared to cases 2 to 4. In Cases 9 to 11, as in Cases 2 to 4, the lance oxygen concentration in the gas carried by the triple pipe lance (first lance) is 55 vol%, and the gas carried by the triple pipe lance (first lance). Since the lance city gas concentration in the inside was set to 12 vol% and the lance city gas concentration in the gas conveyed by the double pipe lance (second lance) was set to 65 vol%, the air permeability deteriorated. On the other hand, in cases 12 to 14, lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 65 vol%, and the triple pipe lance (first lance) conveys the cases 9 to 11. The air permeability was improved by setting the lance city gas concentration in the gas to be 18 vol% and the lance city gas concentration in the gas conveyed by the double pipe lance (second lance) to 75 vol%. That is, even under the condition where the coke strength DI ¹⁵⁰ ₁₅ [%] was reduced to 84.5, the pulverized coal combustibility was improved by increasing the lance oxygen concentration and the lance city gas concentration, and stable operation was possible. .

Further, in the cases 15 to 17, the coke strength DI ¹⁵⁰ ₁₅ [%] was significantly reduced from 84.5 to 82.5 compared to the cases 12 to 14. In cases 15 to 17, as in cases 12 to 14, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 65 vol%, and the gas conveyed by the triple pipe lance (first lance). Since the concentration of the lance city gas was 18 vol% and the concentration of the lance city gas in the gas conveyed by the double pipe lance (second lance) was 75 vol%, the air permeability was greatly deteriorated. On the other hand, in cases 18 to 20, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 72 vol%, and the triple pipe lance (first lance) conveys the cases 15 to 17. The air permeability was improved by setting the lance city gas concentration in the gas to be 24 vol% and the lance city gas concentration in the gas conveyed by the double pipe lance (second lance) to 90 vol%. In this way, even under the condition where the coke strength DI ¹⁵⁰ ₁₅ [%] is reduced to 82.5, the pulverized coal combustibility is improved by increasing the lance oxygen concentration and lance city gas concentration, and stable operation is possible. there were.

  In the cases 21 to 23, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 80 vol% and the gas conveyed by the triple pipe lance (first lance), compared to the cases 12 to 14. Since the lance city gas concentration of 15 vol% and oxygen concentration was greatly increased, the oxygen partial pressure around the pulverized coal increased, resulting in improved oxygen flammability and improved breathability and stability against the base 1 Was in an operational state. Moreover, in cases 24-26, the lance oxygen concentration in the gas conveyed with a triple pipe lance (1st lance) is 50 vol%, and it is conveyed with a triple pipe lance (1st lance) with respect to cases 12-14. Since the lance city gas concentration in the gas was 40 vol% and the city gas concentration was greatly increased, the temperature of the pulverized coal particles was promoted by the rapid combustion of the city gas, and the air permeability was improved by the effect of improving the combustibility. It was in a stable operating state even for 1. Further, in cases 27 and 28, the lance city gas concentration in the gas conveyed by the double pipe lance (second lance) is increased to 85 vol% and 95 vol% with respect to case 26, which increases the city gas concentration. Along with this, the air permeability was improved and the operation was stable. However, the pressure in the tuyere of the blast furnace is about 400 to 430 kPa, and in order to blow gas into the tuyere from the lance, a higher gas pressure is required. Therefore, in order to increase the lance oxygen concentration, high-pressure high-pressure oxygen is necessary, and city gas is also very expensive, so both of them need to be used effectively.

  In cases 29-31, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 85 vol% in the gas conveyed by the triple pipe lance (first lance), compared to cases 18-20. Since the lance city gas concentration of 13 vol% and the oxygen concentration was greatly increased as in cases 21 to 23, the oxygen permeability in the vicinity of the pulverized coal was increased, resulting in an improved oxygen flammability and improved air permeability. The operation state was stable with respect to the base 1. In cases 32 to 34, the lance oxygen concentration in the gas conveyed by the triple pipe lance (first lance) is 50 vol%, and the triple pipe lance (first lance) is conveyed, compared to cases 18 to 20. Since the lance city gas concentration in the gas was 48 vol% and the city gas concentration was greatly increased as in Cases 24-26, the temperature rise of the pulverized coal particles was promoted by the rapid combustion of city gas, and the combustibility improvement effect As a result, the air permeability was improved and the base 1 was in a stable operating state. Further, the cases 35, 36, and 37 are blown by reducing the concentration of the lance city gas in the gas conveyed by the double pipe lance (second lance) to 80 vol%, 70 vol%, and 65 vol% with respect to the case 20. As the city gas concentration decreased, the air permeability deteriorated and the operation became unstable, so the lance city gas concentration blown from the double pipe lance (second lance) The concentration in the gas conveyed by the heavy pipe lance (second lance) is preferably 70 vol% or more. However, as in the cases 21 to 28, since it takes cost to increase the lance oxygen concentration and the lance city gas concentration, both must be used effectively.

As described above, it is desirable that the lance oxygen concentration and the lance city gas concentration blown from the two lances (first and second lances) are as large as possible from the viewpoint of improving pulverized coal combustibility. In order to increase the oxygen concentration, there is a cost associated with increasing the pressure of oxygen. To increase the city gas concentration, it is necessary to increase the city gas, and it is necessary to use a large amount of city gas with a high unit price. Therefore, when the coke strength DI ¹⁵⁰ ₁₅ [%] is 85.5 as in cases 2 to 7, the lance oxygen concentration blown from one triple pipe lance (first lance) is set to 50 to 70 vol. %, The lance city gas concentration may be 10 to 30 vol%, and the lance city gas concentration blown from the other double pipe lance (second lance) may be 60 to 97 vol%.

As described above, in the blast furnace operating method of the present embodiment, the combustion efficiency of the pulverized coal is efficiently improved even under the operating conditions in which the combustion efficiency of the pulverized coal decreases when the coke strength DI ¹⁵⁰ ₁₅ [%] is reduced. Therefore, it is possible to achieve blast furnace operation capable of stabilizing and improving production and reducing exhaust CO ₂ . It was also confirmed that if the operating conditions were constant, the operating specifications could be greatly improved by the blast furnace operating method of the present embodiment. In addition, although there is no special restriction | limiting in the amount of city gas injection, it is necessary to set the usage-amount according to cost.

  1 is a blast furnace, 2 is an air duct, 3 is a tuyere, 4 is a lance, 5 is a raceway

Claims (4)

In the blast furnace operation method in which pulverized coal with an injection amount of 150 kg / t / p or more per 1 ton of pig iron is blown from the blower tuyere with a lance, the strength of the coke charged from the top of the furnace is DI ¹⁵⁰ _{15 according to} the test method described in JISK2151. [%] 87 or less, and the weight ratio of pulverized coal having a particle size of 74 μm or less is 60% or less, the average volatile content of pulverized coal is 25 mass% or less, and the blowing temperature is 1100 ° C. or less. When two or more of the above are satisfied, two lances are used per tuyere, flammable gas and flammable gas are blown from one lance together with pulverized coal, and flammable together with pulverized coal from the other lance. A blast furnace operating method characterized by injecting sex gas.   The concentration of the combustion-supporting gas and the concentration of the flammable gas that are blown together with the pulverized coal from the one lance are 50 to 70 vol% and 10 to 10, respectively, as the concentrations in the gas conveyed by the one lance. 30% by volume, and the concentration of the flammable gas blown together with the pulverized coal from the other lance is 60 to 97% by volume as the concentration in the gas conveyed by the other lance. Item 4. A blast furnace operation method according to Item 1. When the strength of the coke is DI ¹⁵⁰ ₁₅ [%] 85 or less, the concentration of the combustion-supporting gas and the flammable gas that are blown together with the pulverized coal from the one lance are conveyed by the one lance. Concentrations of the flammable gas blown together with the pulverized coal from the other lance are conveyed by the other lance, respectively, as the concentrations in the gas to be discharged are 50 to 80 vol% and 10 to 40 vol%, respectively. The blast furnace operating method according to claim 1, wherein the concentration in the gas is 70 to 97 vol%. When the strength of the coke is DI ¹⁵⁰ ₁₅ [%] 83 or less, the concentration of the combustion-supporting gas and the flammable gas that are blown together with the pulverized coal from the one lance are conveyed by the one lance. The concentrations of the combustible gas are 50 to 90 vol% and 10 to 50 vol%, respectively, and the concentration of the flammable gas blown together with the pulverized coal from the other lance is conveyed by the other lance. The blast furnace operating method according to claim 1, wherein the concentration in the gas is 80 to 97 vol%.

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