JP6458609B2 - Charge determination method and blast furnace operation method of carbon highly reactive charge - Google Patents

Description

  The present invention relates to a method for determining the amount of charged carbon highly reactive charge and a method for operating a blast furnace.

  In the blast furnace, iron-based materials (raw materials containing iron oxide, mainly sintered ore) and coke are charged in layers from the top of the furnace, and hot air is blown from the tuyere at the bottom of the blast furnace. Thereby, the iron oxide descending in the blast furnace is heated and reduced by a reducing gas mainly composed of CO. That is, pig iron is manufactured.

  In such blast furnace operation, a technique for reducing the reducing material ratio has been studied from the viewpoint of energy saving. Here, the reducing material ratio is shown, for example, as the sum of all the reducing material basic units introduced into the blast furnace, that is, the basic unit of coke and the basic unit of pulverized coal blown from the tuyere. Patent Documents 1 to 4 disclose a technique using a carbon highly reactive charge as an example of such a technique. Here, the carbon highly reactive charge contains at least a carbonaceous material and cement. Carbon highly reactive charges often further contain iron oxide. Those containing iron oxide are usually referred to as non-fired carbon-containing agglomerated minerals, and particularly those formed into a spherical pellet using a pelletizer are also referred to as non-fired carbon-containing pellets.

  The carbonaceous material contained in the carbon highly reactive charge is more reactive than coke (that is, gasifies at a lower temperature than coke). Therefore, iron oxide contained in the carbon-reactive charge (hereinafter, such iron oxide is also referred to as “sibling iron oxide”) is rapidly reduced by the carbonaceous material contained in the carbon-reactive charge. The That is, the carbonaceous material contained in the carbon highly reactive charge is gasified at a lower temperature than coke. And sibling iron oxide is reduced with the reducing gas produced | generated by gasification of a carbonaceous material. Therefore, in the blast furnace, the reduction of the sibling iron oxide with the reducing gas is started from the low temperature, so that the utilization rate of the reducing gas is improved.

  Furthermore, the carbon highly reactive charge contains surplus carbon material than the amount of carbon material required for reducing sibling iron oxide to metallic iron. Here, the amount of carbonaceous material required to reduce sibling iron oxide to metallic iron is determined by stoichiometric calculation. The surplus carbon material, that is, the surplus carbon material is an iron-based material existing in the vicinity of the carbon-reactive charge in the blast furnace (hereinafter, this iron-based material is also referred to as “charged iron oxide”). Reduce. That is, surplus carbon material is also gasified at a lower temperature than coke. The charged iron oxide is reduced by the reducing gas generated by gasification of the surplus carbon material. Therefore, in the blast furnace, the reduction of the charged iron oxide with the reducing gas is started from the low temperature. Also in this respect, the utilization rate of the reducing gas is improved.

Examples of carbon highly reactive charges include carbon-containing agglomerated or highly reactive coke. Patent Document 1 discloses an iron ore briquette that utilizes coal meltability for bonding as an example of a coal-containing agglomerated ore. In Patent Document 1, fine ore is mixed with caking coal (carbon material) having a volatile content of 16% or more and a Geseller flow rate of 20 DDPM or more. The mixture is hot-molded at a temperature range of 260 to 550 ° C. and a molding pressure of 20 to 150 MPa, and then degassed for 5 minutes or more in the molding temperature range. Thereby, an iron ore briquette having an apparent density of 2.3 g / cm ³ or more is produced.

Patent document 2 discloses a cement bond carbon-containing agglomerated mineral as an example of a carbon-containing agglomerated mineral. In Patent Document 2, a hydraulic binder is added to a finely divided iron-containing raw material containing 40% by mass or more of iron and a finely divided carbonaceous material containing 10% by mass or more of carbon. Then, by mixing and granulating these raw materials while adjusting the moisture, a cement bond carbon-containing agglomerated mineral with a cold crushing strength of 50 kg / cm ² or more is produced. Moreover, in patent document 2, the particle size of all the raw materials shall be 2 mm or less, the blending ratio of the said pulverized carbonaceous material is adjusted so that the carbon content rate (TC) in all the raw materials may be 15-25 mass%, And the median diameter of this pulverized carbon material shall be 100-150 micrometers.

Patent Document 3 discloses, as an example of highly reactive coke, highly reactive small coke having an average particle size of 38 mm or less produced by blending two or more types of coal having different properties. Specifically, in Patent Document 3, (x) the total volume of pores having a pore diameter of 1 to 10 μm existing in the coke is 25 mm ³ / g or more, and (y) the drum strength index (DI ¹⁵⁰ ₁₅ ) is 70. Disclosed is a highly reactive blob coke as described above.

  Patent Document 4 discloses ferro-coke as an example of highly reactive coke. Ferro-coke increases coke reactivity by using metallic iron as a catalyst. Patent Document 4 also discloses a method for determining a suitable charging amount of ferro-coke. Specifically, in Patent Document 4, when ferro-coke is used as a blast furnace raw material, the amount of carbon in ferro-coke is 1.7 times the amount of solution loss carbon calculated from the blowing amount and the top gas analysis result. Manage the upper limit of ferro-coke usage so that it falls within the range. Patent Document 4 shows that when the blast furnace usage of ferro-coke is about 160 kg / tp, the reducing material ratio reduction effect by ferro-coke can be obtained more efficiently.

  On the other hand, the amount of coke charged is also affected by the reduction characteristics (ie, reducibility) of the iron-based raw material. For this reason, a method for measuring the reduction characteristic value of an iron-based raw material has been proposed. JIS-RI (JIS M8713) is known as a method for measuring the reduction characteristic value of an iron-based raw material. This method is widely known in the steel industry, and the reducibility of the iron-based material is measured by subjecting the iron-based material to CO reduction at a temperature of 900 ° C. for a certain time (3 hours).

Patent Documents 5 and 6 and Non-Patent Document 1 also disclose methods for measuring the reduction characteristic values of iron-based raw materials. The measurement method disclosed in Patent Document 5 is a so-called RA method. Specifically, in Patent Document 5, a reducing gas is brought into contact with a sintered ore to measure reducibility. That is, in a region surrounded by a reduction equilibrium line of calcium ferrite and a reduction equilibrium line of iron oxide with the CO ₂ content ratio and temperature of the reducing gas as variables, and surrounded by a temperature range of 800 ° C. or more and an indirect reduction temperature or less. Measure the reduction rate of the sintered ore.

  The measurement method disclosed in Patent Document 6 is a measurement method using a high-temperature load softening test apparatus, and is also referred to as a large drop test method. Specifically, in Patent Document 6, massive iron ore used in a vertical furnace is charged into a crucible, the crucible is disposed in the electric furnace, and a reducing gas is introduced from below the electric furnace to introduce iron ore. Heat reduction of stones. That is, in Patent Document 6, electric furnaces are arranged in two upper and lower stages, a joint between both electric furnaces is connected by a flange, a reducing gas is introduced from below the lower electric furnace, and the lower electric furnace is connected to an empty While raising the temperature, a crucible charged with iron ore is placed in the upper electric furnace. Then, the temperature of the upper electric furnace and the temperature of the iron ore in the crucible are measured at the same time, and the electric power of the upper electric furnace is adjusted so that the temperature difference becomes a preset constant value.

  The method disclosed in Non-Patent Document 1 is also referred to as a BORIS furnace method or a BIS furnace method. Specifically, in Non-Patent Document 1, the blast furnace lumps are reproduced by forming alternating layers of iron-based raw materials and carbonaceous materials in the test apparatus. Then, the reducibility of the iron-based raw material is measured by measuring the CO utilization rate of the outlet gas corresponding to the blast furnace top gas. In addition, the reducing material ratio can be estimated by calculation based on the result.

JP 11-92833 A JP 2008-95177 A JP 2010-95711 A JP 2011-94182 A JP 2006-249507 A Japanese Patent Laid-Open No. 7-27623

Naito et al. “Technology for improving reaction efficiency in blast furnace by using highly reactive coke”: Iron and Steel, 87 (2001), 357

  As described above, a reduction in the reducing material ratio is expected by charging the carbon highly reactive charge into the blast furnace. On the other hand, it has been found that if the high carbon reactive charge is excessively charged to the blast furnace, the utilization rate of the reducing gas is reduced.

  Therefore, there is a suitable value for the amount of high carbon reactive charge. However, until now, no method has been proposed for predicting a suitable amount of carbon highly reactive charge in advance (before blast furnace operation). Note that the method for measuring the reduction characteristic value of the iron-based raw material is a method for measuring the reduction characteristic value of the iron-based raw material alone or in combination, and predicts a suitable charge amount of the highly reactive carbon charge. Not what you want.

  Patent Document 4 discloses a method for determining a suitable charging amount of ferro-coke. The method disclosed in Patent Document 4 adjusts the ferro-coke charge based on blast furnace operation data, and does not determine a suitable ferro-coke charge before blast furnace operation.

  Therefore, the present invention has been made in view of the above problems. The object of the present invention is to provide a new and improved method for determining the amount of carbon highly reactive charge, which can determine in advance a suitable amount of the highly reactive carbon charge. And it is providing the blast furnace operating method using this.

In order to solve the above-described problems, according to one aspect of the present invention, the charge of the high carbon reactivity charge that determines the amount of charge of the high carbon reactivity charge containing surplus carbon and cement to the blast furnace is provided. This is a method for determining the amount of surplus carbon material when the utilization rate of the reducing gas existing in the blast furnace reaches a maximum value determined depending on the basic unit of surplus carbon material. And specifying the cement basic unit as the maximum amount of cement charged when the reduction gas utilization rate becomes the maximum value determined depending on the cement basic unit, and the upper limit of surplus carbon A step of calculating a threshold which is a ratio of the upper limit charge of surplus carbon and the upper limit charge of cement by dividing the charge by the upper limit charge of cement, and a carbon highly reactive charge If the value obtained by dividing the content of surplus carbon by the content of cement exceeds the threshold, surplus The value obtained by dividing the upper limit charge of the material by the surplus carbon content is the charge of the high carbon reactivity charge, and the surplus carbon content in the high carbon charge is the cement content. When the value divided by the rate is less than the threshold value, the value obtained by dividing the upper limit charge of cement by the cement content is taken as the charge of the high carbon reactivity charge . And a step of determining a charge amount of the charge. A method for determining a charge amount of a highly reactive carbon charge is provided.

  According to another aspect of the present invention, there is provided a blast furnace operating method characterized by charging a blast furnace with a carbon highly reactive charge equal to or less than the charge determined by the above charge determination method. Is done.

  As described above, according to the present invention, of the maximum value of the utilization rate of the reducing gas present in the blast furnace, the surplus carbon material dependent maximum value determined depending on the basic unit of surplus carbon material, and the basic unit of cement It is possible to specify a cement-dependent maximum value determined depending on the value. And in this invention, based on these maximum values, the suitable charge amount of a carbon highly reactive charge is determined. Therefore, it is possible to determine a suitable charge amount of the carbon highly reactive charge in advance.

It is a graph which shows the correlation with a surplus carbon material use basic unit and a reducing gas utilization factor. It is a graph which shows the correlation with a basic unit of cement use, and a reducing gas utilization factor. It is a graph which shows the correlation of a cement usage basic unit, a surplus carbon material usage basic unit, and a gas utilization factor.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Study by the Inventor>
(Background)
The present inventor has examined parameters for determining a suitable charge of the carbon-reactive charge. Hereinafter, the study conducted by the present inventor will be described. As described above, the carbon highly reactive charge includes at least a carbonaceous material and cement. Carbon highly reactive charges often further contain iron oxide. The carbonaceous material contained in the carbon highly reactive charge is more reactive than the coke charged in the blast furnace. The carbon highly reactive charge contains surplus carbon material than the amount of carbon material required to reduce sibling iron oxide to metallic iron. Therefore, the carbonaceous material contained in the carbon highly reactive charge can promote the reduction of the charged iron oxide as well as the sibling iron oxide.

  Thus, reduction of a reducing material ratio is anticipated by charging a highly reactive carbon charge into a blast furnace. On the other hand, it has been found that if the high carbon reactive charge is charged excessively into the blast furnace, the utilization rate of the reducing gas is reduced. Therefore, there is an upper limit for the amount of high carbon reactive charge. However, until now, no method has been proposed for predicting the upper limit of the amount of high carbon reactive charge in advance (before blast furnace operation).

(Examination method)
Then, this inventor paid its attention to the surplus carbon material and cement which are the components of a carbon highly reactive charge. The present inventor conducted the following BIS furnace test in order to confirm whether or not there is a correlation between these basic units (amount charged per ton of pig iron) and the utilization rate of the reducing gas. It was. As test conditions for this BIS furnace test, Table 1 shows the use conditions of the highly reactive carbon charge.

  Moreover, the non-baking carbon-containing agglomerated mineral from which the mass ratio of a surplus carbon material and cement differs was used as a high carbon reactive charge. Here, the carbonaceous material contained in the unfired carbon-containing agglomerated mineral was a coke-based powder having a particle size of 100 μm or less, and the cement was an early-strength Portland cement. The iron oxide used was a mixture of sintered and ore-based powders having a particle size of 100 μm or less at 20:80 (mass ratio). In addition, in order to measure the component of a carbonaceous material raw material and an iron oxide raw material beforehand, and to make it the target carbon-containing agglomerated component, the mixing ratio (mass ratio) of these raw materials was adjusted. Moreover, the particle size in this embodiment is measured using, for example, sieves having different mesh sizes. For example, a sieve having an opening of 100 μm is prepared, and each raw material is passed through this sieve. The raw material remaining on the sieve has a particle size larger than 100 μm, and the measurement sample dropped from the sieve has a particle size of 100 μm or less.

(result)
The results are shown in FIGS. First, FIG. 1 will be described. The horizontal axis in FIG. 1 shows the surplus carbon material use basic unit, that is, the basic unit of surplus carbon material put into the BIS furnace. The basic unit of the surplus carbon material is calculated by multiplying the basic unit of the non-fired carbonaceous agglomerated mineral by the content of the surplus carbon material in the non-fired carbonaceous agglomerated mineral. The vertical axis represents the utilization rate of the reducing gas, that is, the gas utilization rate. The gas utilization rate is a value obtained by dividing the CO ₂ gas concentration in the exhaust gas discharged from the BIS furnace by the sum of the CO ₂ gas and CO gas (reducing gas) concentrations in the exhaust gas.

  Graphs L1-L5 show the correlation between the basic unit of surplus carbon material and the gas utilization rate. The unfired carbon-containing agglomerated mineral corresponding to the graph L1 includes the surplus carbon material and cement at a mass ratio of 10:15, and the unfired carbon-containing agglomerated mineral corresponding to the graph L2 includes the surplus carbon material and cement. At a mass ratio of 10:12. The unfired carbon-containing agglomerated mineral corresponding to the graph L3 includes surplus carbon material and cement in a mass ratio of 10:10, and the unfired carbon-containing agglomerated mineral corresponding to the graph L4 includes the surplus carbon material and cement. At a mass ratio of 10: 7. The unfired carbon-containing agglomerated mineral corresponding to the graph L5 includes surplus carbon material and cement at a mass ratio of 10: 5.

  In the graphs L1 to L3, the utilization rate of the reducing gas was maximized before the surplus carbon basic unit became 20 kg / t. Moreover, when the basic unit of cement when the utilization rate of reducing gas became the maximum was calculated, all were 18 kg / t. In addition, the basic unit of cement is calculated by multiplying the basic unit of the non-fired carbon-containing agglomerated mineral by the content rate of cement in the non-fired carbon-containing agglomerated mineral. Moreover, in the graphs L4 and L5, when the basic unit of surplus carbon material became 20 kg / t, the utilization rate of reducing gas became the maximum. Moreover, the maximum value of the utilization rate of reducing gas became large, so that the mass ratio of the surplus carbon material with respect to cement became large. Furthermore, the larger the mass ratio, the larger the basic unit of surplus carbon material when the utilization rate of the reducing gas is maximized. However, no matter how much the mass ratio was increased, the basic unit of surplus carbon material when the utilization rate of the reducing gas was maximized did not exceed 20 kg / t. Therefore, when the basic unit of surplus carbon material is 20 kg / t or less, the utilization rate of the reducing gas is maximized.

  On the other hand, the horizontal axis of FIG. 2 shows the cement consumption basic unit, that is, the cement basic unit charged into the BIS furnace. The vertical axis represents the utilization rate of the reducing gas, that is, the gas utilization rate. Graphs L6 to L9 show the correlation between the basic unit of cement and the gas utilization rate. The unfired carbon-containing agglomerated mineral corresponding to the graph L6 includes the surplus carbon material and cement at a mass ratio of 10: 5, and the unfired carbon-containing agglomerated mineral corresponding to the graph L7 includes the surplus carbon material and cement. At a mass ratio of 10: 7. The unfired carbon-containing agglomerated mineral corresponding to the graph L8 includes the surplus carbon material and cement in a mass ratio of 10:10, and the unfired carbon-containing agglomerated mineral corresponding to the graph L9 includes the surplus carbon material and cement. At a mass ratio of 10:12.

  In the graphs L6 to L7, the utilization rate of the reducing gas was maximized before the cement unit became 18 kg / t. Moreover, when the basic unit of the surplus carbon material when the utilization rate of reducing gas became the maximum was measured, all were 20 kg / t. Further, in the graphs L8 to L9, the utilization rate of the reducing gas was maximized when the cement basic unit was 18 kg / t. Moreover, the maximum value of the utilization rate of reducing gas became small, so that the mass ratio of the cement with respect to an excess carbon material became large. Furthermore, the larger the mass ratio, the larger the basic unit of cement when the utilization rate of the reducing gas is maximized. However, no matter how much the mass ratio was increased, the cement basic unit when the utilization rate of the reducing gas was maximized did not exceed 18 kg / t. Therefore, when the cement basic unit is 18 kg / t or less, the utilization rate of the reducing gas is maximized.

(Reduction gas utilization rate of surplus carbon material and cement dependent maximum)
According to FIGS. 1 and 2, it can be seen that there is a correlation between the surplus carbon material and cement basic units and the utilization rate of the reducing gas. Furthermore, the maximum value of the reducing gas utilization rate depends on the unit of surplus carbon material (ie, the unit of surplus carbon material becomes a bottleneck) It is also understood that it is classified into a maximum value determined depending on the basic unit of cement (hereinafter also referred to as a “cement dependent maximum value”).

  FIG. 3 summarizes the above findings. Four graphs L10 to L13 passing through the origin in FIG. 3 represent the correlation between the cement basic unit, the surplus carbon material basic unit, and the reducing gas utilization factor for each level. Specifically, the graph L10 shows the correlation between the cement basic unit at level 1 (cement content 5% by mass), the surplus carbon material basic unit, and the utilization rate of the reducing gas, and the graph L11 shows the level 2 (same as 7%). (Mass%) shows the correlation between the cement basic unit, the surplus carbon basic unit, and the utilization rate of the reducing gas. Graph L12 shows the correlation between the basic unit of cement at level 3 (10% by mass), the surplus carbon material unit, and the utilization rate of reducing gas, and graph L13 shows the basic unit of cement at level 5 (15% by mass). Shows the correlation between the surplus carbon intensity and the utilization rate of the reducing gas.

  Specifically, the slopes of the graphs L10 to L13 represent a ratio (κ) obtained by dividing the surplus carbon material content of the unfired carbon-containing agglomerated mineral by the cement content, and the slope of the graphs L10 to L13 increases as κ increases. Will grow. That is, the content rate of the surplus carbon material with respect to cement becomes high, so that the inclination of graph L10-L13 is large. The graphs L10 to L13 include a portion drawn with a solid line and a portion drawn with a broken line. In the part drawn with a solid line, the utilization rate of reducing gas rises according to the increase in the basic unit of surplus carbon material and cement. In the part drawn with a broken line, the utilization rate of a reducing gas reduces according to the increase in the basic unit of surplus carbon material and cement. According to the graphs L10 to L13, the xy plane defined by the vertical axis and the horizontal axis in FIG. 3 is a region where the utilization rate of the reducing gas increases in accordance with the increase in the basic unit of surplus carbon material and cement (hereinafter, “ It is also divided into a region where the utilization rate of the reducing gas decreases in accordance with an increase in the amount of surplus carbon and cement (hereinafter also referred to as a “utilization rate decrease region”). I understand. The utilization rate increasing region and the utilization rate decreasing region are divided by two graphs (ridge lines) L20 and L21. Each graph L20, L21 shows a certain surplus carbon material basic unit and cement basic unit, respectively.

  Further, in graphs L10 and L11 where κ is larger than 1.11 (= 20/18), until the surplus carbon material basic unit reaches 20 kg / t (that is, the surplus carbon material basic unit indicated by graph L20), As the unit and surplus carbon basic unit increase, the utilization rate of reducing gas also increases. And when the surplus carbon material basic unit corresponds to 20 kg / t, the utilization rate of reducing gas becomes the maximum. And after a surplus carbon material basic unit exceeds 20 kg / t, the utilization factor of reducing gas falls with the increase in a cement basic unit and a surplus carbon material basic unit. Therefore, the maximum value of the utilization rate of the reducing gas in the graphs L10 and L11 is the maximum value determined by the surplus carbon material basic unit, that is, the surplus carbon material dependent maximum value. Moreover, the surplus carbon material basic unit which the graph L20 shows shows the upper limit charging amount of surplus carbon material.

  On the other hand, in the graphs L12 and L13 where κ is smaller than 1.11 (= 20/18), until the cement basic unit reaches 18 kg / t (that is, the cement basic unit indicated by the graph L21), the cement basic unit and surplus coal. The utilization rate of reducing gas increases with the increase in the basic unit. When the cement basic unit is equal to 18 kg / t, the utilization rate of the reducing gas is maximized. And after a cement basic unit exceeds 18 kg / t, the utilization factor of reducing gas falls with the increase in a cement basic unit and a surplus carbon material basic unit. Therefore, the maximum value of the utilization rate of the reducing gas in the graphs L12 and L13 is the maximum value determined by the cement unit as a bottleneck, that is, the cement-dependent maximum value. Moreover, the cement basic unit which the graph L21 shows shows the upper limit charging amount of cement.

  In addition, when the cement-dependent maximum values are compared with each other, the cement-dependent maximum value increases as the cement content in the unfired carbon-containing agglomerated mineral decreases (see graphs L8 and L9 in FIG. 2). Therefore, it can be seen that the cement content in the unfired carbon-containing agglomerated mineral is preferably as low as possible from the viewpoint of improving the utilization rate of the reducing gas.

  Further, when κ is 1.11, the cement basic unit is 18 kg / t when the surplus carbon basic unit is 20 kg / t. At this time, the utilization rate of the reducing gas is maximized.

  Thus, the factor which becomes a bottleneck of the utilization rate of a reducing gas changes with ratio (kappa) of the surplus carbon material content rate of a non-baking carbon-containing agglomerate, and a cement content rate. More specifically, a value obtained by dividing the upper limit charging amount of surplus carbon material by the upper limit charging amount of cement is a threshold value (1.11 in the above example) for determining the bottleneck factor. And when ratio (kappa) becomes more than a threshold value, the maximum value of the utilization rate of reducing gas becomes settled by a surplus carbon material basic unit. That is, when the surplus carbon material basic unit becomes the upper limit charging amount (= 20 kg / t), the utilization rate of the reducing gas becomes the maximum value. On the other hand, when the ratio κ is less than the threshold value, the maximum value of the reducing gas utilization rate is determined by the cement basic unit. That is, when the cement basic unit is 18 kg / t, the utilization rate of the reducing gas becomes the maximum value. In addition, when either one of the basic units of surplus carbon and cement reaches the upper limit charge, the utilization rate of the reducing gas even if the other basic unit does not reach the upper limit charge. Is the maximum.

  The upper limit charging amount of surplus carbon material and cement may vary depending on the composition of the unfired carbon-containing agglomerated mineral (for example, types of iron oxide, carbon material and cement, particle size, etc.), operating conditions of the blast furnace, and the like. It is assumed.

  Therefore, the amount of high carbon reactive charge charged to the blast furnace can be determined by the following steps. First, the upper limit charging amount of surplus carbon material and the upper limit charging amount of cement are specified. And a threshold value is calculated by dividing the upper limit charging amount of surplus carbon material by the upper limit charging amount of cement. And the ratio (kappa) of the surplus carbon material content rate and cement content rate of the carbon highly reactive charge actually charged to a blast furnace is calculated. Then, based on the threshold value and the ratio κ, the charge amount of the highly reactive carbon charge is determined. That is, when the ratio κ is equal to or greater than the threshold, the amount of high carbon reactive charge is a value obtained by dividing the upper limit charge of surplus carbon material by the content of surplus carbon material. When the ratio κ is less than the threshold, the amount of high carbon reactive charge is a value obtained by dividing the upper limit amount of cement by the cement content.

(Function)
In addition, this inventor considers the reason for having an upper limit charging amount in the basic unit of surplus carbon material and cement as follows. As described above, the surplus carbon material can promote the reduction of the charged iron oxide. However, if there is too much surplus carbon material charged into the blast furnace, that is, if the basic unit of surplus carbon material exceeds the upper limit charging amount, a sufficient amount of reducing gas is sufficient to reduce the charged iron oxide. It will be generated from the material. That is, the utilization rate of the reducing gas is reduced.

  On the other hand, the cement has a function of binding materials constituting the carbon highly reactive charge. The content of cement is often set to 5 to 15% by mass (% by mass with respect to the total mass of the carbon highly reactive charge) from the viewpoint of securing the strength of the carbon highly reactive charge. Thus, cement is a necessary component to ensure the strength of the carbon highly reactive charge. However, when the basic unit of cement exceeds the upper limit charging amount, the cement causes a dehydration reaction in the blast furnace. Since the dehydration reaction is an endothermic reaction, when the cement undergoes a dehydration reaction, the temperature in the blast furnace decreases. When the temperature in the blast furnace decreases, the utilization rate of the reducing gas decreases.

  Based on the above findings, the present inventor has conceived the method for determining the amount of charged carbon-reactive charges and the method for operating the blast furnace according to the present embodiment.

<2. Carbon highly reactive charge to which this embodiment is applicable>
Next, a highly reactive carbon charge to which the present embodiment can be applied will be described. The carbon highly reactive charge to which this embodiment is applicable is not particularly limited. That is, any carbon-reactive charge may be used as long as it is known. For example, the carbon highly reactive charge may be a carbon-containing agglomerated or ferro-coke. The carbon highly reactive charge may be fired or non-fired. As described above, the carbon highly reactive charge includes at least a carbonaceous material and cement. The carbon highly reactive charge may further contain iron oxide. It is preferable that the carbonaceous material has a higher reactivity than the coke charged into the blast furnace. Examples of the carbon material include pulverized coal. The cement may be, for example, an early-strength Portland cement.

<3. Method for determining the amount of charged carbon highly reactive charge>
Below, the charging amount determination method of the carbon highly reactive charge which concerns on this embodiment is demonstrated. The method for determining the amount of charged carbon-reactive charge includes first and second steps. Hereinafter, each process will be described.

(First step)
In the first step, the upper limit charging amount of surplus carbon material and cement is determined. Specifically, iron oxide, carbonaceous material, and cement constituting the carbon highly reactive charge are prepared, and the carbon highly reactive charge is produced using these materials. Furthermore, a BIS furnace that reproduces the operating conditions of the blast furnace is prepared. And the utilization factor of reducing gas is measured, changing the basic unit of the carbon highly reactive charge charged to a BIS furnace. And based on a measurement result, the graph shown in FIG. 3, ie, the graph which shows the correlation of a cement basic unit, a surplus carbon material basic unit, and the utilization factor of reducing gas is produced.

  And the multiple types of carbon highly reactive charging from which the mass ratio of a surplus carbon material and cement differs is produced. For example, what is necessary is just to produce several types of carbon highly reactive charges which fixed the content rate of the surplus carbon material, and changed the content rate (and content rate of iron oxide) of cement. And the process similar to the above is performed using these carbon highly reactive charges.

  And based on the produced | generated several graph, the two ridgelines which divide a utilization factor raise area | region and a utilization factor reduction area | region are specified. And the surplus carbon material basic unit and cement basic unit which these ridgelines show are made into the upper limit charging amount of a surplus carbon material, and the upper limit charging amount of cement, respectively.

(Second step)
In the second step, the amount of high carbon reactive charge charged in the blast furnace is determined. Specifically, first, the composition of the highly reactive carbon charge charged in the blast furnace is specified. Specifically, the content rate of the surplus carbon material and the content rate of cement in the high carbon reactivity charge are specified.

  Next, the threshold value is calculated by dividing the upper limit charging amount of surplus carbon material by the upper limit charging amount of cement. And the charging amount of a carbon highly reactive charge is determined based on the content rate of the surplus carbon material in the carbon highly reactive charge, the content rate of cement, and a threshold value.

  More specifically, when the value obtained by dividing the content of surplus carbon in the carbon-reactive charge by the cement content is equal to or greater than the threshold, the upper limit charge of surplus carbon is determined as surplus carbon. The value divided by the content of is taken as the amount of high carbon reactive charge. On the other hand, when the value obtained by dividing the surplus carbon content in the carbon-reactive charge by the cement content is less than the threshold value, the value obtained by dividing the cement maximum charge by the cement content. Is the charge of the carbon highly reactive charge.

<4. Blast furnace operation method>
In the blast furnace operating method in the present embodiment, a carbon highly reactive charge equal to or less than the charging amount determined by the above-described charging amount determining method for the carbon highly reactive charge is charged into the blast furnace. As described above, in this embodiment, a suitable charge amount of the carbon highly reactive charge is determined in advance, and the carbon highly reactive charge having the determined charge amount is charged into the blast furnace. Can do. In particular, in the present embodiment, a suitable charge amount of the carbon highly reactive charge is determined in advance regardless of the composition of the carbon highly reactive charge (for example, the type of surplus carbon and cement, mass ratio, etc.). can do. Therefore, the composition of the high carbon reactive charge is determined by various backgrounds such as the raw material balance, the raw material properties, the price, etc. in the steelworks, but the carbon high reactive charge is suitable according to such a composition. The correct charge can be determined.

  Next, in order to confirm that the maximum value of the utilization rate of the reducing gas is determined depending on the basic unit of surplus carbon material and cement, the following examples were performed. In this example, two types of non-fired carbon-containing agglomerates A and B that differ only in the cement content were prepared.

  Here, the carbonaceous materials and iron oxides contained in the unfired carbon-containing agglomerated minerals A and B were the same as those described above. That is, the carbonaceous material was a coke-based powder having a particle size of 100 μm or less. The iron oxide was obtained by mixing sintered and ore-based powders having a particle size of 100 μm or less at a mass ratio of 20:80. The binder was early strong Portland cement. And the non-baking carbon-containing agglomerated minerals A and B were produced by adjusting the mixing ratio (mass ratio) of these raw materials.

  Moreover, the content rate of the surplus carbon material in the non-baking carbon-containing agglomerated minerals A and B was 10 mass%. Moreover, the content rate of the cement in the non-baking carbon-containing agglomerated mineral A was 5 mass%. Moreover, the content rate of the cement in the non-baking carbon-containing agglomerated mineral B was 12 mass%.

And the unbaked carbon-containing agglomerated minerals A and B were thrown into the blast furnace under the charging conditions 1 to 6 shown in Table 2 below. In addition, the operation which does not throw in the non-baking carbon-containing agglomerated minerals A and B as a base operation was also performed. The operating conditions for the base of the blast furnace are shown in Table 3 below. Moreover, when using the non-baking carbon-containing agglomerated minerals A and B on input conditions 1-6, the efficiency of a blast furnace changes. As a result, the hot metal temperature can change. Therefore, when using the unfired carbon-containing agglomerated minerals A and B under the charging conditions 1 to 6, the pulverized coal ratio or the coke ratio was adjusted so that the hot metal temperature coincided with the base condition. Then, the CO ₂ gas concentration and CO gas concentration in the exhaust gas of the blast furnace were measured, and the utilization rate of the reducing gas was calculated based on these measured values. Table 4 shows the measurement results.

  In addition, in a present Example, as the basic unit of the non-baking carbon-containing agglomerated minerals A and B increases, the iron and carbon material charging amount derived from the non-baking carbon-containing agglomerated minerals A and B increase. Therefore, when increasing the use of non-fired carbon-containing agglomerated minerals A and B, the amount of agglomerated ores and pellets is reduced, and coke and pulverized coal (the pulverized coal here is the blast furnace together with hot air from the blast furnace tuyere. To be used) will be reduced. However, the reactivity of the carbonaceous material in the unfired carbon-containing agglomerated minerals A and B is higher than the reactivity of coke and pulverized coal, and as described above, the use of the non-fired carbonized agglomerated minerals A and B As the amount increases, the efficiency of the blast furnace, that is, the reducing material ratio, changes. Therefore, as the amount of unburned coal-containing agglomerated minerals A and B increases, the ratio of reducing material, that is, the amount of all carbon materials (including coke and pulverized coal) in the blast furnace changes to the hot metal temperature of the blast furnace. Changed accordingly. In other words, when starting or using the unfired carbon-containing agglomerated minerals A and B, all the iron and carbonaceous material charges in the blast furnace are charged according to the operating conditions of the base. It was. Since the efficiency of the blast furnace gradually changes due to the effects of the unfired carbon-containing agglomerated minerals A and B, the total amount of carbon material used in the blast furnace (specifically, coke and pulverized coal) Use amount). Thereby, the hot metal temperature was made constant. In other words, the total amount of iron input, the actual amount of carbonaceous material, and the amount of tapping in the blast furnace were made constant under each input condition.

  In the operation using the non-fired carbon-containing agglomerated mineral A having a low cement content, the maximum value of the reducing gas utilization rate was determined by the basic unit of surplus carbon material. Specifically, when the basic unit of surplus carbon material was 20 kg / t, the utilization rate of the reducing gas became the maximum value. Therefore, the upper limit charging amount of surplus carbon material is 20 kg / t, and the surplus carbon material dependent maximum value is 51.4%.

  On the other hand, in the operation using the non-fired carbon-containing agglomerated mineral B having a high cement content, the maximum value of the utilization rate of the reducing gas was determined by the basic unit of the cement. Specifically, when the cement basic unit was 18 kg / t, the utilization rate of the reducing gas became the maximum value. Therefore, the upper limit charging amount of cement is 18 kg / t, and the cement-dependent maximum value is 50.6%. The reason why the surplus carbon material-dependent maximum value and the cement-dependent maximum value are different is that the basic unit of surplus carbon material corresponding to these maximum values is different.

  Thus, according to the present Example, it has confirmed that the maximum value of the utilization rate of reducing gas was determined depending on the surplus carbon material and the basic unit of cement. In the operation using the non-fired carbon-containing agglomerated mineral A, the charging amount of the non-fired carbon-containing agglomerated mineral A may be set to 200 kg / t or less. Here, 200 kg / t is a value obtained by dividing the upper limit charging amount (20 kg / t) of the surplus carbon material by the surplus carbon material content (0.1) in the unfired carbon-containing agglomerated mineral A. Moreover, what is necessary is just to set the charging amount of the non-baking carbon-containing agglomerated B to 150 kg / t or less in the operation using the non-baking carbon-containing agglomerated mineral B. Here, 150 kg / t is a value obtained by dividing the upper limit charging amount of cement (18 kg / t) by the cement content (0.12) in the unfired carbon-containing agglomerated mineral B.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

Claims (2)

A method for determining the amount of carbon highly reactive charge to determine the amount of carbon highly reactive charge containing surplus carbon and cement to the blast furnace,
The surplus carbon material unit when the utilization rate of the reducing gas existing in the blast furnace becomes a maximum value determined depending on the surplus carbon material unit is specified as the upper limit charging amount of the surplus carbon material. And, the step of specifying the basic unit of the cement as the upper limit charging amount of the cement when the utilization rate of the reducing gas becomes a maximum value determined depending on the basic unit of the cement,
The excess of the upper limit charging amount of carbonaceous material is divided by the upper limit charging amount of the cement, the step of calculating the the ratio of the upper limit charging amount of the surplus carbonaceous material as the upper limit charging amount of the cement threshold When,
When the value obtained by dividing the content of the surplus carbon material in the carbon highly reactive charge by the content rate of the cement is equal to or greater than the threshold value, the upper limit charge of the surplus carbon material is determined as the surplus coal. A value obtained by dividing the content of the carbon by the content of the carbon highly reactive charge, and a value obtained by dividing the content of the surplus carbon material in the high carbon reactive charge by the content of the cement. Is less than the threshold, the value obtained by dividing the upper limit amount of the cement by the content of the cement is used as the amount of the high carbon reactive charge, so that the high carbon reactivity is obtained. And a step of determining a charge amount of the charge. A method for determining a charge amount of a highly carbon-reactive charge. A blast furnace operating method characterized by charging a blast furnace with a carbon highly reactive charge equal to or less than the charge determined by the method for determining the charge of a highly reactive carbon charge according to claim 1 .

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