JP2020066753A - Method for operating blast furnace - Google Patents

Abstract

To suppress reduction in the basic unit of blast furnace gas calorific value without increasing the basic unit of carbon consumption.SOLUTION: In a method for operating a blast furnace where a hydrogen-based reduction material is blown from a tuyere, when evaluation value for evaluating the reduction efficiency of the blast furnace is changed, an action for increasing the blowing amount of the hydrogen-based reduction material blown from the tuyere is practiced. For example, correlation information of linearly increasing the basic unit of blast furnace gas calorific value as the blowing amount of the hydrogen-based reduction material is increased has been acquired correspondingly to the evaluation value in advance, and, when the evaluation value is changed to a direction of improving the reduction efficiency, the blowing amount of the hydrogen-based reduction material is determined using the correlation information, and the action can be practiced.SELECTED DRAWING: Figure 6

Description

 The present invention relates to a blast furnace operating method in which a hydrogen-based reducing material is blown from a tuyere.

  Generally, in an integrated steel mill having a blast furnace, a converter, a rolling facility, and an energy supply facility for supplying energy to these, coal is used as a main energy source, and most of the coal is used in the ironmaking process ( It is consumed by the blast furnace, coke oven, and sinter machine), and the by-product gas generated in the ironmaking process is effectively used as an energy source in various equipment in the steelworks.

In recent years, against the background of global environmental problems, demands for energy saving, resource saving, suppression of carbon dioxide (CO ₂ ) generation amount, etc. have been increasing in steelworks as well. Of the CO ₂ generated from the entire steel plant, the large amount of CO ₂ generated from the ironmaking process accounts for the majority of the CO _{2, and} the most CO ₂ emitted from the blast furnace is the largest. Low reducing agent ratio operation is aimed at by reducing efficiency improvement measures such as improvement of reducing property and optimization of distribution of top charge.

  However, when the reduction efficiency of the blast furnace is improved by the method as described above, the calorific value of the gas discharged from the top of the blast furnace (that is, the blast furnace gas) is reduced. Therefore, if the amount of energy supplied to the facilities of the steel mill is less than the demand, energy must be procured from outside. As a result, even if the carbon consumption was reduced in the blast furnace, the reduction of carbon consumption was not always sufficient for the steel mill as a whole.

  Here, in Patent Document 1, in order to prevent a decrease in the calorific value of the gas discharged from the furnace top of the blast furnace, the oxygen concentration in the air blown to the blast furnace is adjusted to 25 to 96%, and the blast furnace gas is adjusted. A method of increasing the calorific value per unit volume of blast furnace gas by reducing the nitrogen concentration in the blast furnace gas and further separating and removing carbon dioxide in the blast furnace gas through a carbon dioxide separator is disclosed.

  However, even if the method described in Patent Document 1 aimed at improving the reduction efficiency is implemented, the calorific value per unit volume of the blast furnace gas increases, but the total calorific value of the blast furnace gas generated during the production of molten iron 1t. (Hereinafter referred to as blast furnace gas calorific value basic unit) will decrease, so if the amount of energy supplied to the various facilities in the steelworks is below the demand as described above, energy must be procured from outside. I have to.

WO2009 / 116672

Ono Yoichi; Iron and Steel Vol. 79 (1993), p N618 Ono Yoichi; Iron and Steel Vol. 79 (1993), p N711 (Especially Section 6.3 Effects of Natural Gas Injection)

  INDUSTRIAL APPLICABILITY The present invention reduces carbon consumption intensity (suppression of increase) and suppression of reduction of blast furnace gas heat generation intensity as operation actions when an evaluation value for evaluating reduction efficiency of a blast furnace such as shaft efficiency changes. The purpose is to realize a method of operating a blast furnace that can achieve both the increase and the increase.

  In order to solve the above problems, the present inventor examined changes in the carbon consumption basic unit and the blast furnace gas calorific value basic unit when blowing the hydrogen-based reducing material from the tuyere. As a result, they have found that the above problems can be solved by using the reduction efficiency of the blast furnace as a management index and controlling the injection amount of the hydrogen-based reducing material according to changes in the reduction efficiency, and have completed the present invention.

  That is, the blast furnace operating method according to the present invention is a method of operating a blast furnace in which a hydrogen-based reducing material is blown from a tuyere, and when the evaluation value for evaluating the reduction efficiency of the blast furnace changes, the hydrogen system blown from the tuyere It is characterized in that an action for increasing the blowing amount of the reducing material is executed. Here, in advance, correlation information in which the blast furnace gas calorific value basic unit linearly increases as the blowing amount of the hydrogen-based reducing material increases is acquired in association with the value of the evaluation value to improve the reduction efficiency. When the evaluation value fluctuates in the direction of performing the action, it is possible to determine the injection amount of the hydrogen-based reducing material using the correlation information and execute the action. When the reduction efficiency is improved for some reason and the blast furnace gas calorific value basic unit is lowered, the action to increase the blowing amount of the hydrogen-based reducing material is executed to suppress the decrease of the blast furnace gas calorific value basic unit. be able to.

  Preferably, the blowing amount of the hydrogen-based reducing material may be determined such that the blast furnace gas calorific value basic unit after performing the action is equal to or higher than the blast furnace gas calorific value basic unit before performing the action. it can.

  Further, in advance, correlation information in which the carbon consumption intensity linearly decreases as the blowing amount of the hydrogen-based reducing material increases is obtained in association with the value of the evaluation value, and the reduction efficiency decreases. When the evaluation value changes, the correlation information can be used to determine the injection amount of the hydrogen-based reducing material, and the action can be executed. When the reduction efficiency decreases for some reason and the carbon consumption basic unit increases, the increase of the carbon consumption basic unit can be suppressed by executing the action of increasing the blowing amount of the hydrogen-based reducing material. Preferably, the blowing amount of the hydrogen-based reducing material can be determined such that the carbon consumption basic unit after the action is executed is equal to or less than the carbon consumption basic unit before the action is executed.

  As the evaluation value, shaft efficiency or furnace top CO gas utilization rate can be used.

  According to the present invention, as the operation action when the evaluation value for evaluating the reduction efficiency of the blast furnace such as the shaft efficiency changes, reduction of the carbon consumption basic unit (suppression of increase) and reduction of the blast furnace gas calorific value basic unit are performed. It is possible to provide a method of operating a blast furnace that can achieve both suppression (increase).

It is a graph which shows the relationship between shaft efficiency and carbon consumption basic unit. It is a graph which shows the relationship between a carbon consumption basic unit and a blast furnace gas calorific value basic unit. It is a graph which shows the relationship between carbon consumption basic unit and blast furnace gas LHV. It is a graph which shows the relationship between the amount of hydrogen gas injection according to shaft efficiency, and the basic unit of calorific value of blast furnace gas. It is a graph which shows the relationship between the amount of hydrogen gas injection according to shaft efficiency, and a carbon consumption basic unit. 4 is a graph for explaining a change in the basic unit of calorific value of blast furnace gas when the amount of hydrogen gas injected is increased (example of increase in shaft efficiency). 4 is a graph for explaining a change in carbon consumption intensity when the hydrogen gas injection amount is increased (example of increase in shaft efficiency). 6 is a graph for explaining a change in carbon consumption intensity when the hydrogen gas injection amount is increased (an example of a decrease in shaft efficiency). 6 is a graph for explaining a change in the basic unit of calorific value of blast furnace gas when the amount of hydrogen gas injected is increased (an example of reduction in shaft efficiency). It is a graph which shows the relationship between the amount of methane gas injection according to shaft efficiency, and a carbon consumption basic unit. It is a graph which shows the relationship between the amount of methane gas injection and the blast furnace gas calorific value basic unit according to shaft efficiency. It is a graph which shows the relationship between the amount of COG gas injection according to shaft efficiency, and carbon consumption basic unit. 6 is a graph showing the relationship between the COG gas injection amount and the blast furnace gas calorific value basic unit according to the shaft efficiency. It is a graph which shows the relationship between the amount of hydrogen gas injection according to (eta) CO, and a blast furnace gas calorific value basic unit. It is a graph which shows the relationship between the amount of hydrogen gas injection according to eta CO, and the carbon consumption basic unit. It is a graph which shows the relationship between the amount of methane gas injection according to eta CO, and the basic unit of calorific value of blast furnace gas. It is a graph which shows the relationship between the amount of methane gas injection according to eta CO, and the carbon consumption basic unit. It is a graph which shows the relationship between the amount of COG gas injection according to ηCO, and the basic unit of calorific value of blast furnace gas. It is a graph which shows the relationship between the amount of COG gas injection according to etaCO, and a carbon consumption basic unit. It is a graph which shows the relationship between the mixed gas injection amount and the blast furnace gas calorific value basic unit according to shaft efficiency. It is a graph which shows the relationship between a mixed gas injection amount and carbon consumption basic unit according to shaft efficiency. 7 is a graph corresponding to FIG. 6 corresponding to a modified example of the first embodiment.

First, the background that led to the creation of the present invention will be described with reference to FIGS. Figure 1 shows the relationship between shaft efficiency and carbon consumption intensity calculated based on the standard conditions in Table 1, where the horizontal axis is shaft efficiency (%) and the vertical axis is carbon consumption intensity (kg / THM). is there. Figure 2 shows the relationship between carbon consumption intensity and blast furnace gas calorific value intensity.The horizontal axis is carbon consumption intensity (kg / THM), and the vertical axis is blast furnace gas heat intensity (Mcal / THM). is there. The shaft efficiency was calculated based on the Rist model described in Non-Patent Documents 1 and 2.

  Here, the shaft efficiency is an index showing the reduction efficiency of the blast furnace that can be changed by controlling the reducibility of the raw material of the blast furnace, controlling the distribution of the charge, etc., and is a Rist model generally used in the analysis of blast furnace operation. Can be defined based on

The Rist model is a process evaluation model that takes into consideration the chemical equilibrium theory for the reduction of FeO iron oxide in addition to the overall mass balance and the partial heat balance in the lower high temperature region of the furnace. In the operating diagram based on the Rist model, the horizontal axis X represents the degree of oxidation of the reducing gas (e.g., (O + H ₂ ) / (C + H ₂ )), and the vertical axis Y represents the degree of oxidation of iron oxide (e.g., O / Fe). ) Is taken into consideration and the mass balance of oxygen at any cross section of the indirect reduction zone is taken into consideration, a linear operation diagram is obtained. It is possible to compare the operating line in the ideal operation and the operating line in the actual operation, and obtain the shaft efficiency from the deviation amount thereof. When the shaft efficiency is 100%, the operating line passes through the point that represents the composition of Wustite reduction (FeO → Fe) called the W point (equilibrium point). When CO gas and H ₂ gas coexist, the W point is determined by a composition obtained by averaging each equilibrium composition of CO reduction and H ₂ reduction of wustite according to the abundance ratio of CO gas and H ₂ gas. The details of the Rist model are described in, for example, Non-Patent Document 1 and the like, and therefore only the above description will be given.

  Referring to FIG. 1, the carbon consumption basic unit (kg / THM) decreases linearly as the shaft efficiency (%) increases. Referring to FIG. 2, the basic unit of calorific value of blast furnace gas (Mcal / THM) increases linearly as the basic unit of carbon consumption (kg / THM) increases. In other words, when the shaft efficiency (%) increases, both the carbon consumption intensity (kg / THM) and the blast furnace gas heat energy intensity (Mcal / THM) both decrease linearly. Here, the carbon consumption basic unit (kg / THM) is the carbon consumption amount (kg) required to produce 1 ton of hot metal. The unit calorific value of blast furnace gas (Mcal / THM) is the total calorific value (Mcal) of blast furnace gas generated when 1 ton of hot metal is produced.

  Here, in the trial calculation of FIG. 1 and FIG. 2, the oxygen enrichment rate was changed from 6 (vol%) to 14 (vol%) by 2 (vol%), and the trial calculation was performed with 5 different oxygen enrichment rates. ing. The basic unit of calorific value of blast furnace gas (Mcal / THM) follows almost the same line regardless of the oxygen enrichment rate if the basic unit of carbon consumption (shaft efficiency) is the same. On the other hand, as is clear from Fig. 3, which shows the relationship between the carbon consumption basic unit (kg / THM) of the blast furnace and the lower heating value per unit volume of the blast furnace gas (hereinafter referred to as LHV), the carbon consumption basic unit (kg (/ THM) decreases the LHV, but increasing the oxygen enrichment ratio can increase the LHV of the blast furnace gas. That is, when the oxygen enrichment rate is increased, the proportion of nitrogen contained in the blast furnace gas is decreased (in other words, the denominator value that defines LHV is decreased), so that LHV is increased. Therefore, the LHV of the blast furnace gas can be increased by increasing the oxygen enrichment rate even if the carbon consumption basic unit (kg / THM) of the blast furnace is decreased (the shaft efficiency is increased). However, since the basic unit of calorific value of blast furnace gas (Mcal / THM) is not affected by the oxygen enrichment rate, the basic unit of calorific value of gas (Mcal / THM) decreases due to the decrease of the basic unit of carbon consumption (kg / THM). Will decrease. In the blast furnace, the oxygen concentration of the gas blown from the tuyere is adjusted by changing the mixing ratio of air and pure oxygen. In this specification, the oxygen enrichment rate defined below is used to represent the mixing ratio of pure oxygen in the air. The oxygen enrichment rate is defined as the concentration (vol%) obtained by subtracting 21 (vol%) from the oxygen concentration in a mixed gas of pure oxygen mixed with air. Therefore, for example, if the oxygen concentration in the mixed gas including pure oxygen mixed with air is 31 (vol%), the oxygen enrichment rate will be 10 (%).

  The present inventor, in order to solve the above problems, by blowing hydrogen, which is an example of a hydrogen-based reducing material, from the tuyere of the blast furnace, blast furnace gas calorific value basic unit (Mcal / THM) and carbon consumption basic unit ( The effect on (kg / THM) was discussed. In the present specification, the hydrogen-based reducing agent refers to hydrogen gas or a reducing agent that decomposes in the raceway portion to generate hydrogen gas when blown into the tuyere of a blast furnace, except for pulverized coal and steam. For example, hydrogen gas, methane gas, coke oven gas (COG gas) and the like. The hydrogen-based reducing material includes not only gas but also solid and liquid.

Figure 4 shows the relationship between the hydrogen gas injection rate and the blast furnace gas calorific value basic unit, which varies depending on the shaft efficiency (%). The horizontal axis is the hydrogen gas injection rate (Nm ³ / THM), and the vertical axis is. It is the basic unit of calorific value of blast furnace gas (Mcal / THM). Figure 5 shows the relationship between the hydrogen gas injection amount and the carbon consumption intensity, which differ depending on the shaft efficiency (%). The horizontal axis is the hydrogen gas injection amount (Nm ³ / THM), and the vertical axis is the carbon consumption. It is a basic unit (kg / THM).

The graphs in FIGS. 4 and 5 can be obtained by using the standard operating conditions and the Rist model described in Non-Patent Document 2. As shown in Fig. 4, when the shaft efficiency (%) is constant, the hydrogen concentration in the furnace top gas increases with an increase in the hydrogen gas injection amount (Nm ³ / THM). / THM) increases linearly. As shown in Fig. 5, when the shaft efficiency (%) is constant, the hydrogen reduction rate increases and the direct reduction rate decreases due to an increase in the hydrogen gas injection amount (Nm ³ / THM). (kg / THM) decreases linearly.

Therefore, if the hydrogen gas injection amount (Nm ³ / THM) is increased while maintaining the shaft efficiency (%), the blast furnace gas calorific value basic unit (Mcal / THM) can be increased. Further, when the shaft efficiency (%) increases, the utilization rate of CO gas and H ₂ gas as the reducing gas increases, so that the blast furnace gas calorific value basic unit (Mcal / THM) decreases.

Since each line corresponding to the shaft efficiency shown in Fig. 4 is linear, the blast furnace gas calorific value basic unit (Mcal / THM) is as a function of the hydrogen gas injection amount (Nm ³ / THM) and the shaft efficiency (%). It can be defined by the equation (1).
Basic unit of calorific value of blast furnace gas = (a _g * ηs + b _g ) * V + (c _g * ηs + d _g ) ・ ・ ・ ・ ・ (Equation 1)
Here, ηs: shaft efficiency (%), V: hydrogen gas injection amount (Nm ³ / THM), and a _g , b _g , c _g and d _g are constants that differ depending on the type of hydrogen-based reducing material. Yes, and for hydrogen gas a _g = -0.0154, b _g = 2.16, c _g = -25.9, d _g = 3657. From equation (1), the basic unit of calorific value of blast furnace gas (Mcal / THM) changes by (a _g * ηs + b _g ) (Mcal / THM) when the hydrogen gas injection amount changes by 1 (Nm ³ / THM). I understand that

It can also be seen that when the shaft efficiency changes by 1 (%), the blast furnace gas calorific value basic unit changes by (a _g * V + c _g ) (Mcal / THM). Therefore, in order to maintain the basic unit of calorific value of blast furnace gas (Mcal / THM) when the shaft efficiency is increased by Δηs (%) with respect to the standard operation, the hydrogen gas injection amount is calculated by the following formula ( According to 2), it is necessary to increase by ΔV (Nm ³ / THM).
ΔV =-(a _g * V + c _g ) * Δηs / (a _g * ηs + b _g ) (Equation 2)
Here, V is the hydrogen gas injection amount (Nm ³ / THM) in the standard operation, ηs is the shaft efficiency (%) in the standard operation, and Δηs is the increase amount (%) of the shaft efficiency from the standard operation.

The above equation (2) can be calculated by solving the following equation (1 ′) for ΔV, ignoring the “Δηs × ΔV term”.
(a _g * ηs + b _g ) * V + (c _g * ηs + d _g )
= (a _g * (ηs + Δηs) + b _g ) * (V + ΔV) + (c _g * (ηs + Δηs) + d _g ) (Equation 1 ')

Similarly, since each line corresponding to the shaft efficiency (%) shown in FIG. 5 is linear, the carbon consumption intensity (kg / THM) is the hydrogen gas injection amount (Nm ³ / THM) and the shaft efficiency (%). As a function, it can be defined by the following equation (3).
Carbon consumption intensity = (a _c * ηs + b _c ) * V + (c _c * ηs + d _c ) (Equation 3)
Where ηs is the shaft efficiency (%), V is the hydrogen gas injection amount (Nm ³ / THM), and a _c , b _c , c _c, and d _c are constants that differ depending on the type of hydrogen-based reducing material. Yes, in the case of hydrogen gas, a _c = -0.0022, b _c = 0, c _c = -3.20, d _c = 725. From the formula (3), the carbon consumption basic unit (kg / THM) varies by (a _c * ηs + b _c ) (kg / THM) per 1 (Nm ³ / THM) injection of hydrogen gas. When the shaft efficiency changes by 1 (%), it changes by (a _c * V + c _c ) (kg / THM). Therefore, for a certain standard operation, when the shaft efficiency decreases by Δηs (%) (Δηs <0), the increment of hydrogen gas injection amount ΔV that makes the carbon consumption basic unit (kg / THM) equal (Nm ³ / THM) is given by equation (4).
ΔV =-(a _c * V + c _c ) * Δηs / (a _c * ηs + b _c ) (Equation 4)
Here, V is the hydrogen gas injection amount (Nm ³ / THM) in the standard operation, ηs is the shaft efficiency in the standard operation, and Δηs is the change amount (%) of the shaft efficiency from the standard operation.

  From the above consideration results, it is sufficient to use the evaluation value for evaluating the reduction efficiency of the blast furnace such as the shaft efficiency as a management index, and control the injection amount of hydrogen-based reducing material such as hydrogen according to the change of the evaluation value. I understand. That is, when the reduction efficiency is improved and the blast furnace gas calorific value basic unit is reduced, the blast furnace gas calorific value basic unit can be maintained by executing the action of increasing the blowing amount of the hydrogen-based reducing material. Further, when the reduction efficiency decreases and the carbon consumption basic unit increases, the carbon consumption basic unit can be maintained by executing the action of increasing the blowing amount of the hydrogen-based reducing material.

Next, an embodiment of the present invention will be described.
(First embodiment)
In this embodiment, monitors the blast furnace shaft efficiency (.eta.s _1), the difference from the predetermined reference of the shaft efficiency _{(ηs 0) (Δηs = ηs} 1 -ηs 0) the management upper limit value (Δηs _-U) When it exceeds, the amount of hydrogen gas blown is increased from the predetermined reference amount of blown gas (V ₀ (Nm ³ / THM)) by ΔV or more, which is determined by the equation (2). The blowing method is not particularly limited, but, for example, it can be blown from the tuyere of the blast furnace via a lance extending into the blow pipe (the same applies to other embodiments).

Based on the past operating results of the blast furnace, the carbon consumption basic unit (kg / THM) and the blast furnace gas calorific value basic unit (Mcal / THM) that should be the standard were determined, and the shaft efficiency (%) and The hydrogen gas injection amount (Nm ³ / THM) can be set as a standard operating condition. The upper limit of the shaft efficiency (%) control is set in consideration of the changes in the basic unit of carbon consumption (kg / THM) and the basic unit of calorific value of blast furnace gas (Mcal / THM), preferably 0.5-2.0%. is there.

In the present embodiment, it is possible to set the operating conditions of Table 1, the amount of hydrogen gas blown = 0 (Nm ³ / THM), and the shaft efficiency of 94% as the standard operation. FIG. 6 corresponds to FIG. 4, and the values of the hydrogen gas injection amount and the blast furnace gas calorific value basic unit at the time of the standard operation are plotted by solid circles. The graph in FIG. 6 corresponds to the correlation information described in claim 2. FIG. 7 corresponds to FIG. 5, and plots the amount of hydrogen gas blown in and the value of carbon consumption intensity at the time of the standard operation by the solid circles.

Here, it is assumed that the shaft efficiency is increased to 96% by improving the reducibility of the raw material or improving the distribution of the charge during the standard operation. From the equation (2), the increase amount of the hydrogen gas injection amount required to maintain the blast furnace gas calorific value basic unit (Mcal / THM) constant is ΔV = 72.5 (Nm ³ / THM). The white circles in FIG. 6 indicate the values of the blast furnace gas calorific value basic unit after increasing the hydrogen gas injection amount. The white circles in FIG. 7 indicate the values of carbon consumption intensity after increasing the amount of hydrogen gas blown.

As shown in FIG. 6, by adding ΔV to the reference hydrogen gas injection amount (0), by injecting hydrogen gas of 72.5 (Nm ³ / THM) or more, the blast furnace gas calorific value basic unit (Mcal / THM) The decrease can be prevented. At this time, as shown in FIG. 7, the carbon consumption intensity decreases.

(Second embodiment)
In this embodiment, monitors the blast furnace shaft efficiency (.eta.s _1), the difference from the predetermined reference of the shaft efficiency _{(ηs 0) (Δηs = ηs} 1 -ηs 0) the management lower limit value (Δηs _-L) When it is less than, the amount of hydrogen gas blown is increased from the predetermined reference amount of blown gas (V ₀ (Nm ³ / THM)) by ΔV or more determined by the equation (4).

Based on the past operating results of the blast furnace, the carbon consumption basic unit (kg / THM) and the blast furnace gas calorific value basic unit (Mcal / THM) that should be the standard were determined, and the shaft efficiency (%) and The hydrogen gas injection amount (Nm ³ / THM) can be set as a standard operating condition. The lower limit of control of shaft efficiency is set in consideration of changes in blast furnace carbon consumption intensity (kg / THM) and blast furnace gas calorific value intensity (Mcal / THM), preferably -0.5 to -2.0%. .

Similar to the first embodiment, it is possible to set the operating conditions in Table 1, the hydrogen gas injection amount = 0 (Nm ³ / THM), and the shaft efficiency of 94% as the standard operation. FIG. 8 corresponds to FIG. 5, and plots the amount of hydrogen gas blown in and the value of carbon consumption basic unit at the time of the standard operation by the solid circles. The graph in FIG. 8 corresponds to the correlation information described in claim 4. FIG. 9 corresponds to FIG. 4, and the values of the hydrogen gas injection amount and the blast furnace gas calorific value basic unit at the time of the standard operation are plotted by the filled circles.

Here, it is assumed that the shaft efficiency is reduced to 92% due to deterioration of the reducibility of the raw material during the standard operation. From the equation (4), the increase amount of the hydrogen gas injection amount required to keep the carbon consumption basic unit (kg / THM) constant is ΔV = 30.9 (Nm ³ / THM). The white circles in FIG. 8 show the values of carbon consumption basic unit (kg / THM) after increasing the hydrogen gas injection amount. The white circles in FIG. 9 indicate the values of the blast furnace gas calorific value basic unit (Mcal / THM) after increasing the hydrogen gas injection amount.

As shown in Fig. 8, by adding ΔV to the standard hydrogen gas injection amount (0) and injecting hydrogen gas of 30.9 (Nm ³ / THM) or more, it is possible to prevent an increase in the carbon consumption basic unit of the blast furnace. You can At this time, as shown in FIG. 9, the basic unit of calorific value of blast furnace gas (Mcal / THM) increases more than in the standard operation.

(Third embodiment)
In this embodiment, methane gas is used as the hydrogen-based reducing material. FIG. 10 corresponds to FIG. 5 and shows the relationship between the methane gas injection amount and the carbon consumption basic unit that differ depending on the shaft efficiency.The horizontal axis is the methane gas injection amount (Nm ³ / THM), and the vertical axis is the vertical axis. The axis is carbon consumption intensity (kg / THM). Fig. 11 corresponds to Fig. 4 and shows the relationship between the methane gas injection amount and the blast furnace gas calorific value basic unit that differ depending on the shaft efficiency, and the horizontal axis is the methane gas injection amount (Nm ³ / THM). The vertical axis is the blast furnace gas calorific value basic unit (Mcal / THM). These graphs can be obtained using the standard operating conditions and the Rist model described in Non-Patent Document 2. The graph shown in FIG. 10 corresponds to the correlation information described in claim 4, and the graph shown in FIG. 11 corresponds to the correlation information described in claim 2.

  Referring to FIG. 10, the hydrogen reduction rate increases and the direct reduction rate decreases due to an increase in the amount of methane gas blown, and thus the carbon consumption basic unit decreases. Referring to FIG. 11, since the hydrogen concentration in the furnace top gas increases as the methane gas injection amount increases, the blast furnace gas calorific value basic unit (Mcal / THM) also increases.

Since each line corresponding to the shaft efficiency shown in FIG. 10 is linear, the carbon consumption basic unit can be expressed by the above formula (3). However, ηs: shaft efficiency (%), V: methane gas injection amount (Nm ³ / THM), and a _c = -0.0055, b _c = 0.351, c _c = -3.20, d _c = 725.

Since each line according to the shaft efficiency shown in FIG. 11 is linear, the blast furnace gas calorific value basic unit (Mcal / THM) can be expressed by the above-mentioned formula (1). However, ηs: shaft efficiency (%), V: methane gas injection amount (Nm ³ / THM), and a _g = -0.0396, b _g = 6.19, c _g = -25.9, d _g = 3657.

  Therefore, in order to maintain the blast furnace gas calorific value basic unit (Mcal / THM) when the shaft efficiency is increased by Δηs (%) for a certain standard operation, the methane gas injection amount is set to the above formula (2). ).

  For a certain standard operation, in order to maintain the carbon consumption rate (kg / THM) when the shaft efficiency decreases, it is necessary to increase the methane gas injection rate according to the above equation (4). .

(Fourth embodiment)
In this embodiment, coke oven gas (hereinafter referred to as COG gas) is used as the hydrogen-based reducing material. COG gas is a gas generated when carbonizing carbon in a coke oven, and contains hydrogen, methane, carbon monoxide, and the like. FIG. 12 corresponds to FIG. 5, and shows the relationship between the COG gas injection amount and the carbon consumption intensity that differ depending on the shaft efficiency, and the horizontal axis is the COG gas injection amount (Nm ³ / THM). The vertical axis is carbon consumption intensity (kg / THM). FIG. 13 corresponds to FIG. 4, and shows the relationship between the COG gas injection amount and the blast furnace gas calorific value basic unit that differ depending on the shaft efficiency, and the horizontal axis indicates the COG gas injection amount (Nm ³ / THM). And the vertical axis is the basic unit of calorific value of blast furnace gas (kg / THM). These graphs can be obtained using the standard operating conditions and the Rist model described in Non-Patent Document 2. Further, the graph shown in FIG. 12 corresponds to the correlation information described in claim 4, and the graph shown in FIG. 13 corresponds to the correlation information described in claim 2.

  Referring to FIG. 12, the hydrogen reduction rate increases and the direct reduction rate decreases due to the increase in the COG gas injection amount, and thus the carbon consumption basic unit decreases. Referring to FIG. 13, since the hydrogen concentration in the furnace top gas increases as the COG gas injection amount increases, the blast furnace gas calorific value basic unit (Mcal / THM) also increases.

Since each line corresponding to the shaft efficiency shown in FIG. 12 is linear, the carbon consumption basic unit (kg / THM) can be represented by the above-mentioned formula (3). However, ηs: shaft efficiency (%), V: COG gas injection amount (Nm ³ / THM), and a _c = -0.0032, b _c = 0.192, c _c = -3.20, d _c = 725.

Since each line according to the shaft efficiency shown in FIG. 13 is linear, the blast furnace gas calorific value basic unit (Mcal / THM) can be expressed by the above-mentioned formula (1). However, ηs: shaft efficiency (%), V: COG gas injection amount (Nm ³ / THM), and a _g = -0.0227, b _g = 3.53, c _g = -25.9, d _g = 3657.

  Therefore, in order to maintain the blast furnace gas calorific value basic unit (Mcal / THM) when the shaft efficiency is increased, with respect to a certain standard operation, the COG gas injection amount is calculated according to the above equation (2). Need to increase.

  For a certain standard operation, in order to maintain the carbon consumption intensity (kg / THM) when the shaft efficiency decreases, it is necessary to increase the COG gas injection amount according to the above equation (4). is there.

(Fifth embodiment)
In the above-described embodiment, the shaft efficiency is used as the evaluation value for evaluating the reduction efficiency, but the present invention is not limited to this, and the furnace top CO gas utilization rate (hereinafter, referred to as ηCO) can also be used. ηCO is the ratio of CO ₂ to the total amount of CO and CO ₂ contained in the top gas can be calculated by analyzing the top gas.

FIG. 14 corresponds to FIG. 4, and shows the relationship between the hydrogen gas injection amount and the blast furnace gas heat generation amount basic unit (Mcal / THM), which differ depending on ηCO, and the horizontal axis represents the hydrogen gas injection amount (Nm ³ / THM), and the vertical axis is the blast furnace gas calorific value basic unit (Mcal / THM). Fig. 15 corresponds to Fig. 5 and shows the relationship between the hydrogen gas injection amount and the carbon consumption basic unit that differ depending on ηCO, the horizontal axis is the hydrogen gas injection amount (Nm ³ / THM), and the vertical axis is The axis is carbon consumption intensity (kg / THM). FIG. 16 corresponds to FIG. 14, and methane gas is used as the hydrogen-based reducing material. FIG. 17 corresponds to FIG. 15, and methane gas is used as the hydrogen-based reducing material. FIG. 18 corresponds to FIG. 14, and COG gas is used as the hydrogen-based reducing material. FIG. 19 corresponds to FIG. 15, and COG gas is used as the hydrogen-based reducing material.

The graphs shown in FIGS. 14, 16 and 18 correspond to the correlation information described in claim 2, and the graphs shown in FIGS. 15, 17 and 19 correspond to the correlation information described in claim 4. The above equations (2) and (4) can be read as the following equations (2 ′) and (4 ′), respectively, and applied to this embodiment.
ΔV =-(a _g * V + c _g ) * ΔηCO / (a _g * ηCO + b _g ) (Equation 2 ')
Here, V is the injection amount of the hydrogen-based reducing agent in the standard operation (Nm ³ / THM), ηCO is the furnace top CO gas utilization rate in the standard operation (%), ΔηCO is the furnace top CO gas utilization rate from the standard operation. The amount of increase (%).
ΔV =-(a _c * V + c _c ) * Δηco / (a _c * ηco + b _c ) (Equation 4 ')
Here, V is the injection amount of the hydrogen-based reducing agent in the standard operation (Nm ³ / THM), ηCO is the furnace top CO gas utilization rate in the standard operation (%), ΔηCO is the furnace top CO gas utilization rate from the standard operation. The amount of increase (%).

That is, ηCO of the blast furnace is monitored, and when the difference from the predetermined reference ηCO (ΔηCO) exceeds the control upper limit value, the injection amount of the hydrogen-based reducing material is changed to the predetermined reference injection amount ( From V ₀ (Nm ³ / THM)), it is possible to increase by ΔV or more determined by the equation (2 ′). Further, ηCO of the blast furnace is monitored, and when the difference from the predetermined reference ηCO is below the control lower limit value, the hydrogen gas injection amount is set to the predetermined reference injection amount (V ₀ (Nm ³ / THM)), it can be increased by ΔV or more determined by the equation (4).

As the evaluation value for evaluating the reduction efficiency, in addition to the shaft efficiency and the furnace top CO gas utilization rate (ηCO), CO reduction rate, H ₂ reduction rate, direct reduction rate and the like can be used.

(Modification 1)
In the above-described first to fourth embodiments, any one of hydrogen gas, methane gas, and COG gas was used as the hydrogen-based reducing material, but the present invention is not limited to this, and a mixed gas of these and modified hydrocarbons. Quality gas can also be used. The values of the coefficients in the above equations (1) and (3) are shown in Tables 2 and 3 below. Since the reformed gas of hydrocarbons also contains CO gas, the coefficient value for CO gas is also shown.

  When the mixed gas is blown as the hydrogen-based reducing material, the above-mentioned coefficients may be weight-averaged according to the mixing ratio (volume ratio) of the respective gases forming the mixed gas. FIGS. 20 and 21 show the results when a mixed gas of methane gas (50% by volume) and hydrogen gas (50% by volume) were blown in as a hydrogen-based reducing material, and FIG. 20 corresponds to FIG. 4. 21 corresponds to FIG.

  As described above, FIG. 20 and FIG. 21 can be drawn by weighted averaging each coefficient of methane gas and hydrogen gas by volume ratio. The blast furnace operating method using FIGS. 20 and 21 is the same as that of the above-described embodiment, and thus detailed description thereof is omitted.

(Modification 2)
In the above-described first embodiment, the hydrogen gas injection amount is set so that the blast furnace gas calorific value basic unit (Mcal / THM) becomes equal to or higher than the standard operation, but the present invention is not limited to this. For example, as shown in FIG. 22, 1200 (Mcal / THM), which is lower than the basic unit of calorific value of blast furnace gas at the time of standard operation, is set as the lower limit value, and the shaft efficiency is 94 (%) to 96 (%). Hydrogen gas may be blown so as to satisfy the above lower limit when the temperature rises to. In this case, it is clear from Fig. 7 that the carbon consumption intensity (kg / THM) is lower than in the standard operation. Similarly, as a modified example of the second embodiment, a carbon consumption basic unit which is slightly higher than that in the standard operation is set as the upper limit value, and when the shaft efficiency is lowered, hydrogen gas is set so as to satisfy the upper limit value. You may blow in.

Claims (6)

In the blast furnace operating method in which the hydrogen-based reducing material is blown from the tuyere,
A method for operating a blast furnace, which comprises performing an action of increasing an amount of the hydrogen-based reducing material blown from the tuyere when an evaluation value for evaluating the reduction efficiency of the blast furnace changes. In advance, the correlation information in which the blast furnace gas calorific value basic unit increases linearly as the blowing amount of the hydrogen-based reducing material increases is obtained in association with the value of the evaluation value,
When the evaluation value is changed in a direction in which the reduction efficiency is improved, the injection amount of the hydrogen-based reducing material is determined by using the correlation information, and the action is executed. Blast furnace operation method.   It is characterized in that the blowing amount of the hydrogen-based reducing material is determined so that the basic unit of calorific value of blast furnace gas after performing the action is equal to or higher than the basic unit of calorific value of blast furnace gas before performing the action. The blast furnace operating method according to claim 2. In advance, the correlation information in which the carbon consumption basic unit linearly decreases as the blowing amount of the hydrogen-based reducing material increases is acquired in association with the value of the evaluation value,
When the evaluation value changes in a direction in which the reduction efficiency decreases, the injection amount of the hydrogen-based reducing material is determined using the correlation information, and the action is executed. Blast furnace operation method.   5. The blowing amount of the hydrogen-based reducing material is determined so that the carbon consumption intensity after performing the action is equal to or less than the carbon consumption intensity before performing the action. Blast furnace operation method described. 6. The blast furnace operating method according to claim 1, wherein the evaluation value is a shaft efficiency or a furnace top CO gas utilization rate.