Gas reduction rate measurement method, blast furnace operation method, direct reduction shaft furnace operation method, and iron raw material

Abstract

The present invention provides a gas reduction rate measurement method capable of properly measuring the gas reduction rate, including the effect of stagnation of the reduction reaction, for iron raw materials used in the iron-making process, a blast furnace operation method, a direct reduction shaft furnace operation method, and iron raw materials. A method for measuring a gas reduction rate of an iron raw material used in an iron-making process by a gas reducing agent, comprising: setting a measurement time t (min) for measuring the gas reduction rate of the iron raw material to a time t calculated by the following formula (1): ret A method for measuring the gas reduction rate, with a value of 0.9 or more. t ret =5×d / (X CO -2×X CO2 +2×X H2 -4×X H2O ) × exp(6000 / T) ···(1) Here, T is the reduction temperature (K), d is the average particle size (mm) of the iron raw material, and X CO is the CO concentration of the gaseous reducing agent, and X CO2 is the CO2 concentration of the gas reducing agent, and X H2 is the H2 concentration of the gas reducing agent, and X H2O means the H2O concentration % of the gaseous reducing agent.

Description

[Technical field]

[0001] The present invention relates to a method for measuring the gas reduction rate of an iron raw material used in an iron-making process using a blast furnace, a direct reduction shaft furnace, or the like, a method for operating a blast furnace, a method for operating a direct reduction shaft furnace, and the iron raw material. [Background technology]

[0002] The blast furnace process (a method of producing molten iron using a blast furnace) accounts for more than 70% of crude steel production in Japan. However, the blast furnace process also has the aspect of being a process that emits a lot of CO2 because it consumes a large amount of coal as a reducing agent to melt and reduce the iron oxide in the iron ore. In light of the current social situation regarding environmental issues, reducing CO2 emissions from the blast furnace process, or reducing CO2 emissions by switching to processes other than the blast furnace process, is an urgent issue for the steel industry.

[0003] There are several ways to reduce CO2 emissions in the blast furnace process, one of which is to use hydrogen as a gas reducing agent. Methods proposed for using hydrogen include simply blowing hydrogen into the tuyere together with the blast air, blowing hydrogen into the tuyere as a specific compound (e.g., hydrocarbons such as methane), and blowing hydrogen-based reducing gas into a part other than the tuyere.

[0004] Here, one of the reasons why CO2 emissions in the blast furnace process are reduced by injecting a gas reducing agent such as hydrogen into the blast furnace is that the gas reduction rate of iron oxide in the iron raw material is increased.

[0005] Iron raw materials charged into a blast furnace are reduced mainly by two methods. The first is gas reduction using gas reducing agents such as CO and hydrogen. The second is smelting reduction using carbon (C) in coke, which is a solid reducing agent. In the blast furnace process, gas reduction progresses as the raw materials (iron raw materials and solid reducing agent) descend from the top to the bottom of the blast furnace, and then the iron raw materials that were not reduced by gas reduction melt and are melted and reduced by the solid reducing agent, completing the reduction reaction.

[0006] The difference between gas reduction and smelting reduction lies in the amount of heat generated by the reduction reaction. Gas reduction is a reduction reaction that generates (or absorbs) a small amount of heat. In contrast, smelting reduction is a reduction reaction that absorbs a large amount of heat. By increasing the proportion of gas reduction using a gas reducing agent (such as hydrogen gas), it is possible to reduce the proportion of smelting reduction using a solid reducing agent. This makes it possible to reduce the amount of heat required per ton of molten iron in a blast furnace, reducing the amount of solid reducing agent (carbon) used and lowering CO2 emissions.

[0007] Another example of a conversion to steelmaking processes other than the blast furnace method is the direct reduction method (a method of producing reduced iron using a direct reduction shaft furnace). Unlike the blast furnace method, the direct reduction method produces reduced iron instead of molten iron, but like the blast furnace method, it is a steelmaking process that can produce iron from raw iron.

[0008] In the direct reduction method, coke is not required, and the iron raw material is reduced by a preheated gas reducing agent. By using hydrogen as the gas reducing agent, it is possible, in principle, to carry out an ironmaking process that does not emit CO2.

[0009] In the direct reduction method, the reduction reaction of the iron raw material proceeds only through gas reduction. The product, reduced iron, is melted and refined in a downstream process such as an electric furnace. If the reduction rate achieved (final reduction rate) of the reduced iron is low (iron oxide remains) at this time, problems such as a decrease in the yield of molten steel and damage to refractories will occur. The reduction rate achieved by the reduced iron is required to be around 80% to 90%.

[0010] In the direct reduction process, the gas reduction rate of the iron raw material can be improved by reducing the passage speed of the iron raw material through the direct reduction shaft furnace and extending the reduction time. However, reducing the passage speed through the furnace leads to a decrease in production volume.

[0011] As described above, in the blast furnace method and the direct reduction method in which a gas reducing agent (hydrogen gas, etc.) is injected, it is important to improve the rate of gas reduction of the iron raw material. However, it is known that even when gas reduction of an iron raw material, such as an agglomerate ore (pellets or sintered ore), is carried out by a gas reducing agent at a temperature (e.g., 900°C) at which the agglomerate ore does not start to melt, the reduction reaction based on the gas reduction stagnates when the reduction reaction reaches a predetermined state (reduction rate of 70%). Specifically, there is a structure inside the agglomerate ore that prevents gas reduction, and the reduction reaction of the gas reduction stagnates due to the influence of the structure. The stagnation of the reduction reaction refers to a sudden decrease in the rate of change of the reduction rate per hour (reduction rate).

[0012] Also, a method based on "Iron ore-reducibility test (JIS M 8713:2009)" is known as a method for measuring the gas reduction rate of iron raw materials. However, in this method, the reducibility of iron raw materials is evaluated by performing a reduction reaction for 180 minutes on a sample with an average particle size of 20 mm under conditions of 30% carbon monoxide (CO) gas, 70% nitrogen (N2) gas, and a temperature of 900°C (1173K), and then evaluating the gas reduction rate. The average evaluation value (reduction rate) under these conditions is around 60% because the measurement time is short, and it is not possible to evaluate the gas reduction rate (70% or more) at which the reduction reaction stagnates.

[0013] Although many methods for improving the gas reduction rate of iron raw materials have been proposed, little research has been done on methods for avoiding stagnation of the reduction reaction or on methods for measuring an appropriate gas reduction rate. Patent Document 1 discloses a method for suppressing stagnation of the reduction reaction at high temperatures by adding dolomite or limestone to pellets to increase the melting point of the pellets. Patent Document 2 discloses a structure of sintered ore with a high SiO2 content that is excellent in the reduction reaction at high temperatures while maintaining the strength of the sintered ore. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Special Publication No. 3-77853 [Patent Document 2] Patent No. 7035869 [Non-patent literature]

[0015] [Non-Patent Document 1] Iron and Steel, Vol. 79 (1993) 9, N618 [Non-Patent Document 2] Iron and Steel, Vol.79(1993)10, N711 [Non-Patent Document 3] Iron and Steel, Vol. 73 (1987) 15, p. 1956 [Non-Patent Document 4] Iron and Steel, Vol.69(1983)3, p.363 Summary of the Invention [Problem to be solved by the invention]

[0016] However, the method disclosed in Patent Document 1 is suitable for suppressing the stagnation of the reduction reaction when the iron raw material is in a high temperature state, and it is difficult to apply it to the stagnation of the reduction reaction in a temperature state where the iron raw material does not start to melt. In addition, the method disclosed in Patent Document 2 can obtain sintered ore with excellent reduction reaction, but there is no description about the stagnation of the reduction reaction related to the temperature state, and it is difficult to apply it to the stagnation of the reduction reaction in a temperature state where the iron raw material does not start to melt. Furthermore, in Patent Document 2, the target reduction rate in a high temperature state is set to 71%, which is about the same as the reduction rate (reduction rate 70%) at which the stagnation of the reduction reaction based on the above-mentioned gas reduction is observed, so it cannot be said that Patent Document 2 takes into consideration the stagnation of the reduction reaction based on the above-mentioned gas reduction.

[0017] The present invention has been made in consideration of the above circumstances, and has an object to provide a gas reduction rate measurement method, a blast furnace operation method, a direct reduction shaft furnace operation method, and iron raw materials, which are capable of properly measuring the gas reduction rate, including the influence of stagnation of the reduction reaction, for iron raw materials used in an iron-making process. [Means for solving the problem]

[0018] The gist and configuration of the present invention to solve the above problems are as follows. [1] A method for measuring a gas reduction rate of an iron raw material used in an iron-making process by a gas reducing agent, the method comprising the steps of: ret × 0.9 or more. t ret =5×d / (X CO -2×X CO2 +2×X H2 -4×X H2O ) × exp(6000 / T) ···(1) Here, T is the reduction temperature (K), d is the average particle size (mm) of the iron raw material, and X CO is the CO concentration of the gaseous reducing agent, and X CO2 is the CO2 concentration of the gas reducing agent, and X H2 is the H2 concentration of the gas reducing agent, X H2O means the H2O concentration % of the gas reducing agent. [2] The measurement time t (min) is the time t ret The gas reduction rate measuring method according to [1], wherein the gas reduction rate is 1.3 or less. [3] The gas reduction rate measuring method according to [1] or [2], wherein the total concentration of the CO concentration and the H2 concentration in the gas reducing material is 30 mass% or more and 100 mass% or less. [4] The gas reduction rate measuring method according to [1] or [2], wherein the average particle size of the iron raw material is 9 mm or more and 21 mm or less. [5] The method for measuring a gas reduction rate according to [1] or [2], wherein the reduction temperature is 1073 K or higher and 1273 K or lower. [6] The gas reduction rate is measured using the gas reduction rate measurement method described in [1] or [2], and the measured gas reduction rate is 95% or more. The iron raw material is charged into a blast furnace, and a gas reducing agent is added to the blast furnace at a rate of 100 Nm 3 A blast furnace operating method in which molten iron is produced by supplying more than 1 / t of iron. [7] A method for operating a direct reduction shaft furnace, comprising measuring a gas reduction rate using the gas reduction rate measuring method according to [1] or [2], and charging an iron raw material having the measured gas reduction rate of 95% or more into the direct reduction shaft furnace to produce reduced iron. [8] A ferrous raw material that is gas-reduced by a gas reducing agent in a steelmaking process, wherein the measurement time t (min) for measuring the gas reduction rate of the ferrous raw material by the gas reduction is calculated by the following formula (1): ret × 0.9 or more, and the measured gas reduction rate is 95% or more. t ret =5×d / (X CO -2×X CO2 +2×X H2 -4×X H2O ) × exp(6000 / T) ···(1) Here, T is the reduction temperature (K), d is the average particle size (mm) of the iron raw material, and X CO is the CO concentration of the gaseous reducing agent, and X CO2 is the CO2 concentration of the gas reducing agent, and X H2 is the H2 concentration of the gas reducing agent, X H2O means the H2O concentration % of the gas reducing agent. Effect of the Invention

[0019] According to the present invention, the gas reduction rate, including the effect of stagnation of the reduction reaction, of an iron raw material used in an iron-making process can be properly measured. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a charging state of a gas reducing agent and a solid reducing agent in a blast furnace. [Diagram 2] FIG. 2 is a diagram showing the relationship between the amount of gas reducing agent and the optimum gas reduction rate. [Diagram 3] FIG. 3 is a diagram showing the test results of gas reduction of the sample (agglomerate ore) under the test condition A. [Figure 4] FIG. 4 is a diagram showing the test results of gas reduction of the sample (agglomerate ore) under the test condition B. [Diagram 5] FIG. 5 shows the results of a gas reduction test carried out on the sample (agglomerate ore 1) under different test conditions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the present invention will be described through embodiments of the present invention.

[0022] The present invention relates to a reduction reaction carried out on iron raw materials including agglomerates, lump ores, etc. (hereinafter referred to as "iron raw materials") by a gas reducing agent blown into a furnace in an iron-making process, for example as shown in FIG. 1, and in particular to a method for measuring the gas reduction rate of the iron raw materials.

[0023] The present inventors first focused on the relationship between the amount of gas reducing agent injected (hereinafter referred to as the "amount of gas reducing agent") and the gas reduction rate. In particular, they focused on the relationship with the amount of gas reducing agent with respect to the gas reduction rate when the total amount of the solid reducing agent used (hereinafter referred to as the "amount of solid reducing agent") and the amount of gas reducing agent is minimized (hereinafter referred to as the "optimum gas reduction rate"). Then, the amount of gas reducing agent Nm 3 The optimum gas reduction rate (%) for the total amount of reducing materials per tonne of steel was calculated based on heat and mass balance calculations taking into account the reduction equilibrium of wustite with carbon monoxide (CO) and hydrogen gas (see Non-Patent Documents 1 and 2). Here, the optimum gas reduction rate refers to a value calculated each time based on the amount of each reducing material (amount of solid reducing material and amount of gas reducing material) used, as a value for minimizing the total amount of reducing materials (total amount of solid reducing material and amount of gas reducing material) from the viewpoint of the heat supply in the furnace and the function of the reducing materials.

[0024] Here, the gas reduction rate means the ratio of gas reduction to all reduction reactions of the iron raw material. The gas reduction agent may include not only gases that function as gas reduction agents themselves, such as hydrogen and carbon monoxide (CO), but also gases that function as gas reduction agents via oxidation reactions or thermal decomposition reactions, such as methane and ammonia.

[0025] The amount of gas reducing agent is, for example, 1 Nm 3When methane is blown into the furnace, it reacts with the oxygen in the blast, producing a gas of 1 Nm 3 of carbon monoxide and 2Nm 3 In this case, the total amount of gas reducing agent is 3 Nm 3 The amount of 1Nm 3 The amount of gas reducing agent when blowing methane into the furnace is 3 Nm 3 and count it.

[0026] Also, for example, 1 Nm 3 When ammonia was blown into the furnace, the ammonia was 1.5 Nm 3 of hydrogen and 0.5Nm 3 Nitrogen does not function as a reducing agent, so it is decomposed into 1Nm 3 The amount of gas reducing agent when blowing ammonia into the furnace is 1.5 Nm 3 and count it.

[0027] Similarly, when the gaseous reducing agent contains impurities such as nitrogen, the amount of the gaseous reducing agent is counted based on the amount of the gaseous reducing agent generated in the furnace. Therefore, the gaseous reducing agent may be a mixture of multiple types of gases.

[0028] The temperature of the gas reducing agent is preferably 1300°C or less, which is the hot air temperature in the furnace, and is more preferably 500°C or less in order to increase the optimum gas reduction rate above the state where the reduction reaction by gas reduction stagnates (reduction rate of 70%), and is even more preferably 100°C or less.

[0029] Furthermore, the concentration of the gaseous reducing agent that actually contributes to gaseous reduction among the gaseous reducing agents injected into the furnace is preferably 90% by volume or more, and more preferably 95% by volume or more.

[0030] The optimum gas reduction rate for the amount of gas reducing material was calculated with the thermal reserve zone temperature set at 1000°C, the blast temperature set at 1100°C, and the blast moisture content set at 20g / Nm 3In a blast furnace with a heat loss of 100Mcal / t, the gas reduction ratio that minimizes the amount of solid reducing material was calculated when gas reducing material (assuming 100% room temperature hydrogen) was blown in. In this case, the shaft efficiency was set to a maximum value of 0.95 [-: dimensionless number].

[0031] Figure 2 shows the gas reducing agent amount Nm 3 The relationship between the gas reduction rate and the optimum gas reduction rate is shown in Fig. 2. 3 It can be seen that the optimum gas reduction rate exceeds 75% when the amount of gas reducing agent exceeds 100 Nm 3 It can be confirmed that when the amount of gas reducing agent exceeds 800 Nm3 / t, the optimal gas reduction rate exceeds the state where the reduction reaction stagnates due to the gas reduction of the iron raw material (reduction rate of 70%). In addition, as the amount of gas reducing agent increases, the amount of CO2 reduction in blast furnace operation also increases, but considering the point at which no change in the amount of CO2 reduction is observed, the amount of gas reducing agent is set to 800 Nm3 / t. 3 / t or less, and 600Nm 3 It is more preferable that the ratio is 1 / t or less.

[0032] In the direct reduction method, the gas reduction rate of the reduced iron product must be 80% to 90%, as described above. Therefore, if the gas reduction reaction stagnates when the gas reduction rate reaches 70% during the gas reduction of the iron raw material, this leads to deterioration of the product quality or a decrease in productivity.

[0033] Next, the inventors prepared various agglomerates as iron raw materials and performed reduction reaction tests under various conditions on the prepared iron raw materials (agglomerates), thereby examining an appropriate method for measuring the gas reduction rate in the gas reduction of iron raw materials.

[0034] Specifically, the chemical composition was adjusted by changing the agglomerate ore mix, and the firing time and oxygen concentration of the blast gas were also changed to produce the agglomerates. The agglomerates were produced by mixing the blended raw materials, granulating them, and firing them in a pot test. The agglomerates were also classified by particle size and used in the reduction test.

[0035] Then, the prepared iron raw material (agglomerate) was heated and then maintained at a constant temperature while a gas reducing agent was passed through it to measure the change in mass, and a reduction rate curve was obtained based on the change in mass. At this time, the reduction temperature, the composition of the gas reducing agent, and the sample particle size were changed to measure the change in mass of each agglomerate. Furthermore, tests were also conducted under different test conditions for the same sample (agglomerate).

[0036] Regarding the test conditions of gas reduction using a gas reducing agent, the reduction temperature was changed in the range of 1073-1173K, and the average particle size of the sample (agglomerate ore) was changed in the range of 10-20mm. Here, the average particle size means the harmonic mean diameter. Regarding the composition of the gas reducing agent, carbon monoxide (CO) was changed in the range of 0-95 mass%, carbon dioxide (CO2) was changed in the range of 0-5 mass%, hydrogen (H2) was changed in the range of 0-100 mass%, and nitrogen (N2) was changed in the range of 0-70 mass%.

[0037] Other test conditions for gas reduction using a gas reducing agent included a maximum reduction time of 5 hours (300 minutes), a flow rate of the gas reducing agent of 15 L / min, and an initial mass of the sample (agglomerated ore) of 150 g.

[0038] Based on the time series change in the mass of the iron raw material (agglomerated ore) detected during the test, the time series change in the gas reduction rate R during the test was calculated. Specifically, the gas reduction rate R was calculated by expressing the proportion of oxygen removed from the iron raw material (agglomerated ore) as a mass fraction % and converting the change in mass into the gas reduction rate R using the following formula (2) based on "JIS M 8713:2021 Iron ore - Measurement method for reducibility."

[0039]

number

[0040] Here, the reduction rate curve obtained in the gas reduction test was analyzed using a reduction model that does not consider the stagnation of the reduction reaction (unreacted nucleus model: see Non-Patent Document 3) to calculate the gas reduction rate at which the reduction reaction begins to stagnate (hereinafter referred to as the "stagnation gas reduction rate"). Specifically, the reduction model was fitted using the reduction rate curve that was the result of the test, and it was considered that the reduction reaction began to stagnate at the gas reduction rate at which the value of the reduction rate curve and the value of the reduction model began to diverge.

[0041] Based on the time when the gas reduction rate (stagnation gas reduction rate) at which it can be determined that the reduction reaction has started to stagnate is reached, the time at which the effect of the stagnation of the reduction reaction can be evaluated is determined as the time t at which the stagnation of the reduction reaction can be confirmed. ret (min).

[0042] The time t at which the stagnation of the reduction reaction can be confirmed ret (min) can be calculated from the following formula (1) based on the composition of the gas reducing material used in the gas reduction. In formula (1), (X CO -2×X CO2 +2×X H2 -4×X H2O ) is a coefficient and may be set based on the fact that the relationship between the reduction rates of carbon monoxide (CO) and hydrogen (H2) is approximately 1:2, and that the relationship between the compositions of CO / CO2 or H2 / H2O at Fe-FeO equilibrium is approximately 2:1. The "6000" in exp(6000 / T) may be determined by experimentally investigating the temperature dependence of several sintered ores. In addition, the "5" in 5×d may be determined by performing reduction experiments (with specified gas components and temperatures) multiple times, determining the test time that is confirmed to exceed the stagnation gas reduction rate under each condition, and setting the coefficient to "5" so as not to exceed that time. t ret =5×d / (X CO -2×X CO2 +2×X H2 -4×X H2O ) × exp(6000 / T) ···(1)

[0043] In equation (1), T is the reduction temperature (K), d is the average particle size of the raw iron (mm), and X CO is the CO concentration of the gas reducing agent, X CO2 is the CO2 concentration of the gas reducing agent, and X H2 is the H2 concentration of the gas reducing agent, X H2O means the HO concentration (%) of the gas reducing agent.

[0044] Table 1 shows the composition ratio of the sample (agglomerate ore) used in the gas reduction test. Table 2 shows the test conditions for the gas reduction test. As shown in Table 2, in the test conditions (A to D), the composition ratio of the gas reducing material used in the gas reduction test, the reduction temperature in the gas reduction test, and the particle size of the sample (agglomerate ore) were changed. ret " is a value calculated by applying the ratio of the component composition of the gas reducing material to formula (1). Note that "Test condition D" shown in Table 2 indicates the test condition equivalent to the conventional gas reduction test condition "Iron ore - reducibility test (JIS M 8713:2009)".

[0045] [Table 1]

[0046] [Table 2]

[0047] Figure 3 shows the test results of gas reduction of the sample (agglomerate) based on test condition A. Test condition A is set to a reduction temperature of 900°C (1173K) and a particle size of the sample (agglomerate) of 12mm. The gas reduction material was composed of 100% by volume of hydrogen (H2). The gas reduction test based on test condition A was carried out using agglomerates 1 to 3 shown in Table 1 as samples.

[0048] As shown in Figure 3, under test condition A, "time t ret " is 50 min. And, as shown in Figure 3, "time t retBy setting the "time t" to 50 min, the reduction rate curves of the gas reduction rates of the agglomerates 1 to 3 could be measured including the stagnant gas reduction rate and over the time when the change in the gas reduction rate subsided. In other words, the gas reduction rates of the samples, the agglomerates 1 to 3, could be properly measured including the effect of the stagnation of the reduction reaction. ret The gas reduction degrees of agglomerates 1 to 3 could be determined from the values ​​on the reduction degree curve in

[0049] FIG. 4 shows the test results of gas reduction of the sample (agglomerate) under test condition B. Test condition B is set to a reduction temperature of 900°C (1173K) and a particle size of the sample (agglomerate) of 10mm. The gas reduction material was composed of 95% carbon monoxide (CO) and 5% carbon dioxide (CO2). The gas reduction test under test condition B was carried out using agglomerates 1, 4 to 6 shown in Table 1 as samples.

[0050] As shown in Table 2, under test condition B, "time t ret " is 98 min. And, as shown in Figure 4, "time t ret By setting the "time t" to 98 min, the reduction rate curves of the gas reduction rates of the agglomerates 1 and 4 to 6 could be measured including the stagnant gas reduction rate and over the time when the change in the gas reduction rate subsided. In other words, the gas reduction rates of the samples, the agglomerates 1 and 4 to 6, could be properly measured including the effect of the stagnation of the reduction reaction. ret The gas reduction degrees of agglomerates 1, 4 to 6 could be determined from the values ​​on the reduction degree curve in

[0051] FIG. 5 shows the results of gas reduction tests carried out on the sample agglomerate 1 under different test conditions. The upper limit of the test time was set to 180 minutes, which is the measurement time specified in the conventional gas reduction test conditions "Iron ore - reducibility test (JIS M 8713:2009)". As shown in FIG. 5, under test conditions A to C, the "time t retBy measuring the gas reduction rate of the agglomerate 1 based on the time of "reduction reaction", the reduction rate curve of the gas reduction rate could be measured including the stagnant gas reduction rate (85%) of the agglomerate 1 and over the time when the change in the gas reduction rate subsides. In other words, the gas reduction rate of the sample agglomerate 1 could be properly measured including the effect of stagnation of the reduction reaction.

[0052] Specifically, it was possible to measure the gas reduction rate of the agglomerate 1 when gas reduction was performed using the gas reducing agent under each of the test conditions A to C. That is, for each of the test conditions A to C, the gas reduction rate was measured at each "time t ret The values ​​on each reduction degree curve in "1" could be regarded as the gas reduction degree of the agglomerate 1 under each test condition.

[0053] On the other hand, in the test condition D, the upper limit of the measurement time was 180 minutes, and therefore the gas reduction of the agglomerated ore 1 did not proceed until the stagnant gas reduction rate was reached at which the reduction reaction stagnates. Therefore, the reduction rate curve of the gas reduction rate could not include the stagnant gas reduction rate, and further, it was not possible to perform measurement until the point at which the change in the gas reduction rate settled down.

[0054] As shown in Figures 3 to 5, even if the composition and properties of the iron raw material (agglomerate) as a sample change and the test conditions are changed, the "time t ret ", the gas reduction test was performed based on the stagnation gas reduction rate, and the gas reduction rate was measured over the period until the change in the gas reduction rate settled down. Therefore, the "time t ret By conducting a gas reduction test based on ", the gas reduction rate of the iron raw material (agglomerate ore) can be properly measured, including the effect of stagnation of the reduction reaction. ret The value on the reduction rate curve in the above experiment was determined to be the gas reduction rate of the iron raw material (agglomerate ore).

[0055] In addition, the measurement time t (min) for measuring the gas reduction rate of the iron raw material is t ret It is desirable that the time is t ret-10% time (time t ret × 0.9) as a standard, and for the reduction rate curve of the gas reduction rate at the subsequent measurement time t (min), a value at any point on the reduction rate curve may be taken as the gas reduction rate of the iron raw material. In this case, a more accurate gas reduction rate can be obtained for the gas reduction rate of the test target iron raw material. Then, the measurement time t (min) for measuring the gas reduction rate of the iron raw material is set to time t ret × 0.9 and the value on the reduction rate curve at that time is specified as the gas reduction rate of the iron raw material, it can be calculated as a gas reduction rate that exceeds the stagnant gas reduction rate of the iron raw material.

[0056] In addition, when using a reduction rate curve to measure the gas reduction rate of iron raw materials (agglomerates), if the time for measuring the gas reduction rate is too long, the gas reduction rate of the iron raw materials will approach 100%, making it difficult to accurately detect the gas reduction rate from an operational standpoint. For this reason, the measurement time t (min) for measuring the gas reduction rate of the iron raw materials should be set to t ret It is desirable for the time to be less than ×1.3.

[0057] The total concentration of the CO concentration and the H concentration in formula (1) is preferably 30 mass% or more as specified in the conventional gas reduction test conditions "Iron ore - reducibility test (JIS M 8713:2009)", and from the viewpoint of the test time of the gas reduction rate of the iron raw material, it is more preferably 80 mass% or more and 100 mass% or less.

[0058] The reduction temperature in formula (1) is preferably set to 1073 K or more and 1273 K or less, which are the main temperatures in the blast furnace method and the direct reduction method, and more preferably 1073 K or more and 1173 K or less from the viewpoint of reducing the cost of reduction testing. The average particle size of the iron raw materials in formula (1) is preferably set to 9 mm or more and 21 mm or less, which is the range of the average particle size of the iron raw materials that can actually be charged in the blast furnace method and the direct reduction method, and more preferably 9 mm or more and 15 mm or less from the viewpoint of the test time for the gas reduction rate of the iron raw materials. Here, the average particle size of the iron raw materials means the harmonic mean diameter.

[0059] And, as mentioned above, at time t ret The value on the reduction degree curve at may be specified as the gas reduction degree of the iron raw material, and the iron raw material with the specified gas reduction degree may be applied to the iron making process. Also, at time t ret ×0.9 or more time (time t ret The value on the reduction rate curve at a subsequent measurement time t (min) based on a time of -10% relative to the reduction rate of the iron raw material is identified as the gas reduction rate of the iron raw material, and the iron raw material with the identified gas reduction rate may be applied to an iron making process.

[0060] Furthermore, prior to the operation of the iron-making process, an iron raw material with a specified gas reduction rate may be prepared in advance. Specifically, the iron raw material is subjected to gas reduction by a gas reducing agent in the iron-making process, and the measurement time t (min) for measuring the gas reduction rate of the iron raw material by gas reduction is set to a time t calculated by the formula (1). ret The gas reduction rate is measured as above, and an agglomerate having the measured gas reduction rate of 95% or more is prepared and may be used in the subsequent operation of the iron-making process.

[0061] As described above, the gas reduction rate measurement method, blast furnace operation method, direct reduction shaft furnace operation method, and iron raw material according to the present embodiment can properly measure the gas reduction rate of iron raw materials used in iron-making processes including the blast furnace method and the direct reduction method, including the influence of stagnation of the reduction reaction. By using the properly measured iron raw materials in the iron-making process, it is possible to reduce CO2 emissions, suppress a decrease in productivity in the iron-making process, and improve the quality of the product obtained through the iron-making process. EXAMPLES

[0062] Hereinafter, examples carried out based on the gas reduction rate measuring method according to this embodiment and an iron raw material will be described.

[0063] In the examples, a virtual physical blast furnace and a virtual physical direct reduction shaft furnace implemented in cyberspace were used to confirm whether it was possible to measure an appropriate gas reduction rate when using iron raw materials (agglomerates) with different compositions and properties.

[0064] The gas reduction rate of the agglomerated ore was measured by two methods: a conventional measurement method (iron ore-reducibility test (JIS M 8713:2009)) and the gas reduction rate measurement method according to the present invention. For the reduction behavior of the gas reduction in the virtual physical blast furnace and the virtual physical direct reduction shaft furnace, non-patent document 4 was referred to, and calculation parameters were determined so as to be consistent with the test results (Tables 1 and 2, Figs. 3 to 5). In addition, in Tables 3 and 4, the conventional measurement method (JIS M 8713:2009) is indicated as "gas reduction rate (conventional)", and the gas reduction rate measurement method according to the present invention is indicated as "gas reduction rate (present invention)".

[0065] First, the gas reduction rate in the blast furnace process was measured as follows. For the standard operation 1, which is the standard for the CO2 reduction rate, the hot air blast temperature was 1100°C, the oxygen concentration was 21%, and the blast moisture was 20g / Nm 3 The heat loss was 100 Mcal / t, and the solid reducing agent ratio, which is the total of the pulverized coal rate and the coke rate, was 487 kg / t. In addition to the operating conditions in the standard operation 1, the standard operation 2 to 3, the comparative example 1, and the invention examples 1 to 3 were carried out by injecting a gas reducing agent from the tuyere.

[0066] The measurement of the gas reduction rate (the present invention) was carried out based on the conditions of "Test Condition B" shown in Table 2. For this reason, the time t ret The gas reduction time was set to 100 min. Specifically, the gas reduction rate at the time of 100 min was determined as the gas reduction rate of each agglomerate. Table 3 shows the results of the measurement of the gas reduction rate in the blast furnace process.

[0067] [Table 3]

[0068] As shown in Table 3, the gas reduction ratio of the agglomerate 1 used in the standard operations 1 to 3 was 70% when measured based on the gas reduction ratio (conventional) and was 90% when measured based on the gas reduction ratio (present invention). The stagnant gas reduction ratios shown in Table 3 indicate the stagnant gas reduction ratios obtained for the agglomerates used in each example.

[0069] The "evaluation" in Table 3 was based on a comparison of the gas reduction rates of multiple agglomerates, and was evaluated as "good (○)" when the CO2 reduction rate was improved by using agglomerates with a high gas reduction rate. Any other results were evaluated as "bad (×)."

[0070] In the standard operations 1 to 3, the amount of gas reducing agent was changed while the operation mode was hot air blowing. As shown in Table 3, the CO2 reduction rate improved as the amount of gas reducing agent increased.

[0071] In Comparative Example 1, the gas reduction rate (conventional) is higher than that in Standard Operation 2, which has the same amount of gas reducing material. However, the gas reduction rate (conventional) is lower than the stagnant gas reduction rate, and the CO2 reduction rate is about the same as that in Standard Operation 2.

[0072] In the invention example 1, when compared with the standard operation 2 in which the amount of gas reducing material is the same, the gas reduction rate (conventional) is the same, but the gas reduction rate (present invention) is a higher value. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the CO2 reduction rate is a higher value than the standard operation 2. In the invention example 2, when compared with the standard operation 3 in which the amount of gas reducing material is the same, the gas reduction rate (conventional) is the same, but the gas reduction rate (present invention) is a higher value. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the CO2 reduction rate is a higher value than the standard operation 3. In the invention example 3, when compared with the standard operation 2 in which the amount of gas reducing material is the same, both the gas reduction rate (conventional) and the gas reduction rate (present invention) are high values. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the CO2 reduction rate is a higher value than the standard operation 2.

[0073] From the above, the gas reduction ratio measuring method according to the present invention can properly measure the gas reduction ratio of the iron raw material (agglomerate ore) including the influence of the stagnation of the reduction reaction. Then, by using the iron raw material (agglomerate ore) whose gas reduction ratio has been properly measured by the gas reduction ratio measuring method according to the present invention, it becomes possible to reduce CO2 emissions.

[0074] More specifically, the gas reduction rate of the iron raw material (agglomerate ore) can be properly measured up to a range exceeding the stagnant gas reduction rate, so that evaluation (measurement) can be made taking into account the influence of stagnation of the reduction reaction in the gas reduction. When iron raw material (agglomerate ore) selected based on the gas reduction rate (conventional) is charged into a blast furnace, the reduction in CO2 emissions is small, but when iron raw material (agglomerate ore) selected based on the gas reduction rate (present invention) is charged into a blast furnace, the reduction in CO2 emissions can be increased. For example, as a blast furnace operation method, the gas reduction rate is measured using the gas reduction rate measurement method according to the present invention, iron raw material (agglomerate ore 5 or 6) having a measured gas reduction rate of 95% or more is charged into the blast furnace, and a gas reducing agent is supplied to the blast furnace at a rate of 100 Nm 3 / t or more to produce molten iron.

[0075] Next, the measurement of the gas reduction ratio in the direct reduction process was carried out as follows. As shown in Table 4, the production amount of reduced iron in the standard operation was set to 1.0. Then, the agglomerated ore 1 used in the standard operation was replaced with other agglomerated ores having different gas reduction ratios (conventional) and (present invention), and the change in the product reduction ratio was confirmed, and also whether or not the appropriate gas reduction ratio could be measured was confirmed.

[0076] The measurement of the gas reduction rate (the present invention) was carried out based on the conditions of "Test Condition B" shown in Table 2. For this reason, the time t ret The gas reduction time was set to 100 min. Specifically, the gas reduction rate at the time of 100 min was determined as the gas reduction rate of each agglomerate. Table 4 shows the results of the measurement of the gas reduction rate in the direct reduction method.

[0077] [Table 4]

[0078] As shown in Table 4, the gas reduction ratio of the agglomerate 1 used in the standard operation was 70% when measured based on the gas reduction ratio (conventional) and 90% when measured based on the gas reduction ratio (present invention). The stagnant gas reduction ratios shown in Table 4 indicate the stagnant gas reduction ratios obtained for the agglomerates used in each example.

[0079] In Table 4, the "evaluation" was evaluated as "good (○)" when the product reduction rate or production volume improved compared to the standard operation. If the result was anything other than that, it was evaluated as "bad (×)."

[0080] In Comparative Example 1, the gas reduction rate (conventional) is higher than the standard operation. However, the gas reduction rate (conventional) is lower than the stagnant gas reduction rate, and the product reduction rate is about the same as the standard operation.

[0081] In the invention example 1, when compared with the standard operation, the gas reduction rate (conventional) is the same, but the gas reduction rate (present invention) is a higher value. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the product reduction rate is higher than the standard operation. In the invention example 2, when compared with the standard operation, the gas reduction rate (conventional) is the same, but the gas reduction rate (present invention) is a higher value. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the product reduction rate becomes the same as the standard operation, and the production volume becomes a high value. In the invention example 3, when compared with the standard operation, both the gas reduction rate (conventional) and the gas reduction rate (present invention) are high values. And, as the gas reduction rate (present invention) exceeds the stagnant gas reduction rate, the product reduction rate is higher than the standard operation.

[0082] As described above, the gas reduction ratio measuring method according to the present invention can properly measure the gas reduction ratio of the iron raw material (agglomerate ore) including the influence of the stagnation of the reduction reaction. By using the iron raw material (agglomerate ore) whose gas reduction ratio has been properly measured by the gas reduction ratio measuring method according to the present invention, it is possible to improve the product reduction ratio or production volume.

[0083] More specifically, the gas reduction rate of the iron raw material (agglomerated ore) can be properly measured up to a range exceeding the stagnant gas reduction rate, so that evaluation (measurement) can be performed taking into account the influence of stagnation of the reduction reaction in the gas reduction. When the iron raw material (agglomerated ore) selected based on the gas reduction rate (conventional) is directly charged into the reduction shaft furnace, the effect of improving the product reduction rate cannot be obtained. However, when the iron raw material (agglomerated ore) selected based on the gas reduction rate (present invention) is directly charged into the reduction shaft furnace, the product reduction rate or production amount can be improved. For example, as a method of operating the direct reduction shaft furnace, the gas reduction rate may be measured using the gas reduction rate measurement method according to the present invention, and the iron raw material (agglomerated ore 5 or 6) having the measured gas reduction rate of 95% or more may be charged into the direct reduction shaft furnace to produce reduced iron.

Claims

1. A method for measuring a gas reduction rate of an iron raw material used in an iron-making process by a gas reducing agent, comprising: The measurement time t (min) for measuring the gas reduction rate of the iron raw material is a time t calculated by the following formula (1): ｒｅｔ × 0.9 or more, The reduction temperature is 1073K or more and 1173K or less, The gaseous reducing agent has a CO concentration of 0 to 95 mass%, a CO 2 concentration of 0 to 5 mass%, an H 2 concentration of 0 to 100 mass%, an H 2 O concentration of 0 to 5 mass%, and an N 2 concentration of 0 to 70 mass%, The iron raw material has a composition including 0.40 to 14.41 mass% FeO, 0.82 to 12.47 mass% CaO, 2.51 to 5.77 mass% SiO 2 , 0.39 to 1.83 mass% Al 2 O 3 , 0.07 to 0.53 mass% MgO, and 55.15 to 68.07 mass% T.Fe; The method for measuring a gas reduction rate, wherein the average particle size of the iron raw material is 10 mm or more and 20 mm or less. t ｒｅｔ =5×d / (X ＣＯ -2×X ＣＯ２ +2×X Ｈ２ -4×X Ｈ２Ｏ )×exp(6000 / T) ・・・(1) Here, T is the reduction temperature K, d is the average particle size mm of the iron raw material, and X ＣＯ is the CO concentration (%) of the gas reducing agent, X ＣＯ２ is the gaseous reducing agent CO ２ Concentration%, X Ｈ２ is the H of the gas reducing agent ２ Concentration%, X Ｈ２Ｏ is the H of the gas reducing agent ２ O concentration %.

2. The measurement time t (min) is the time t ｒｅｔ The gas reduction rate measuring method according to claim 1, wherein the gas reduction rate is 1.3 or less.

3. The CO concentration and the H concentration in the gas reducing agent ２ The gas reduction rate measuring method according to claim 1 or 2, wherein the total concentration of the gas reduction rate and the concentration of the oxidizing agent is 30 mass% or more and 100 mass% or less.

4. The gas reduction rate is measured using the gas reduction rate measuring method according to claim 1 or 2, and the measured gas reduction rate is 95% or more. The iron raw material is charged into a blast furnace, and a gas reducing agent is supplied to the blast furnace at a rate of 100 Nm ３ A blast furnace operating method in which molten iron is produced by supplying more than 100 t of iron.

5. 3. A method for operating a direct reduction shaft furnace, comprising: measuring a gas reduction rate using the gas reduction rate measuring method according to claim 1 or 2; and charging an iron raw material having the measured gas reduction rate of 95% or more into the direct reduction shaft furnace to produce reduced iron.

6. An iron raw material that is gas-reduced by a gas reducing agent in an iron-making process, The measurement time t (min) for measuring the gas reduction rate of the gas reduction of the iron raw material is calculated by the following formula (1): ｒｅｔ × 0.9 or more, The reduction temperature is 1073K or more and 1173K or less, The gaseous reducing agent has a CO concentration of 0 to 95 mass%, a CO 2 concentration of 0 to 5 mass%, an H 2 concentration of 0 to 100 mass%, an H 2 O concentration of 0 to 5 mass%, and an N 2 concentration of 0 to 70 mass%, The iron raw material has a composition of 0.40 to 14.41 mass% FeO, 0.82 to 12.47 mass% CaO, 2.51 to 5.77 mass% SiO 2 , 0.39 to 1.83 mass% Al 2 O 3 , 0.07 to 0.53 mass% MgO, and 55.15 to 68.07 mass% T.Fe, The gas reduction rate of the iron raw material is measured when the average particle size of the iron raw material is set to 10 mm or more and 20 mm or less, and the measured gas reduction rate of the iron raw material is 95% or more. t ｒｅｔ =5×d / (X ＣＯ -2×X ＣＯ２ +2×X Ｈ２ -4×X Ｈ２Ｏ )×exp(6000 / T) ・・・(1) Here, T is the reduction temperature K, d is the average particle size mm of the iron raw material, and X ＣＯ is the CO concentration (%) of the gas reducing agent, X ＣＯ２ is the gaseous reducing agent CO ２ Concentration%, X Ｈ２ is the H of the gas reducing agent ２ Concentration%, X Ｈ２Ｏ is the H of the gas reducing agent ２ O concentration %.

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