JP3642027B2 - Blast furnace operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blast furnace operating method in which a sintered ore is manufactured, and a blast furnace charging raw material including the sintered ore is charged into a blast furnace to operate the blast furnace.
[0002]
[Prior art]
The blast furnace iron making process, which is the mainstream of the iron making process, relies on carbon materials such as coal for about 80% of the total energy required. After being used for hot metal production etc., it is released out of the system in the form of CO + CO _2. The inside CO is used as another heat source and is finally discharged in the state of CO ₂ .
[0003]
On the other hand, in recent years, with the development of industry, energy consumption has increased dramatically, the problem of global warming has become obvious, and CO ₂ reduction has become a social need. According to the 1997 “Kyoto Protocol”, CO ₂ emissions in Japan are required to be reduced by 6% by 2010 from the 1990 level. Therefore, even in the steel industry, which accounts for over 11% of final energy consumption in Japan, there is a strong demand for CO ₂ reduction. Among these, the ironmaking process including blast furnaces is the largest energy consumption sector, and CO ₂ in the ironmaking process. Reduction is extremely important.
[0004]
[Problems to be Solved by the Invention]
However, at present, there is no specific guideline for reducing CO ₂ emissions in the sintering machine and blast furnace total.
[0005]
The present invention was made in view of such circumstances, and an object thereof is to provide a blast furnace method which can effectively reduce the CO ₂ emissions of the sintering machine and blast furnace total.
[0006]
[Means for Solving the Problems]
As a result of various studies to solve the above-mentioned problems, the inventors have conducted preliminary reduction of the sintered ore to increase the carbonaceous basic unit of the sintering machine and reduce the fuel ratio in the blast furnace. There it is possible to increase the fuel ratio decrease amount in the blast furnace than the baked coal ZaiHara units rise during sintering if 30% or more, and found that it is possible to reduce the amount of CO ₂ commensurate therewith . That is, in the sintering machine and blast furnace, to a predetermined amount less CO ₂ emissions than the amount of CO ₂ that occurs in the case of using the not pre-reduced as sintering ore is charged into the blast furnace, 30 It has been found that the preliminary reduction of the sintered ore may be performed at a predetermined reduction rate of at least% .
[0007]
The present invention has been completed based on such knowledge, and includes a step of sintering a raw material containing fine iron ore and a carbonaceous material by a sintering machine to produce a sintered ore, and the sintered ore. A blast furnace operating method including a step of charging a blast furnace charging raw material into the blast furnace and operating the blast furnace, wherein the preliminary reduction rate of the sintered ore is 30% or more. in manner, and the sintering machine and blast furnace, than the amount of CO ₂ that occurs in the case of using the not pre-reduced as sintering ore is charged into the blast furnace, a predetermined amount or more small amount of produced CO ₂ Thus , a blast furnace operating method characterized by being controlled as described above is provided.
[0008]
In this case, the predetermined amount is preferably 10%.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described.
In the present invention, the preliminary reduction of the sintered ore is performed at a reduction rate such that the CO ₂ emission amount is reduced by a predetermined amount or more as the total of the sintering machine and the blast furnace. First, how the operation of the blast furnace is changed by using the partially reduced sintered ore thus preliminarily reduced will be described using a list model based on the overall material and heat balance for the blast furnace.
[0010]
FIG. 1 is a diagram showing a gas temperature distribution inside a blast furnace, and FIG. 2 is a list diagram showing a blast furnace operation when a partially reduced sintered ore is used.
[0011]
In FIG. 1, the gas temperature inside the blast furnace is about 150-200 ° C. at the top of the furnace and 2000-2400 ° C. at the tuyere. In addition, the shaft portion has a constant temperature region of approximately 1000 ° C. called a so-called heat storage zone. In this heat preservation zone, iron oxide exists in a gas composition and a reduction stage slightly deviating from the FeO-Fe reduction equilibrium. In FIG. 2, the upper horizontal axis represents the degree of oxidation of the gas in the blast furnace (in other words, the oxygen atomic ratio O / C with respect to carbon atoms). The degree of oxidation of the gas is 1 when the gas composition is only CO at the bottom of the blast furnace, and is 2 when the gas moves to the upper part while reducing iron oxide and finally becomes CO ₂ (+ N ₂ ). is there. On the other hand, the vertical axis represents the oxygen atomic ratio (O / Fe) to iron atoms. The state with the highest degree of oxidation at the time of charging is Fe ₂ O ₃ (oxidation degree = 1.5). As the reduction proceeds sequentially in the blast furnace, Fe ₃ O ₄ (oxidation degree = 1.33), FeO ( The degree of oxidation = 1.05), and finally metal iron (degree of oxidation = 0). Moreover, if this is expressed in terms of a reduction rate, Fe ₂ O ₃ (reduction rate = 0%), Fe ₃ O ₄ (reduction rate = 11.3%), FeO (reduction rate = 30%), metallic iron (reduction rate = 100%).
[0012]
The lower part of FIG. 2 is a reduction equilibrium diagram of iron oxide by CO. The horizontal axis represents the degree of gas oxidation as described above, and the vertical axis represents the reduction equilibrium temperature. When the temperature of the heat preservation zone is 1000 ° C. from FIG. 1, the degree of gas oxidation (O / C) at the Fe-FeO reduction equilibrium at this temperature is obtained from the lower stage of FIG. Since the oxidation degree of the ore (FeO) is 1.05, the W point in the upper part of FIG. 2 is obtained.
[0013]
On the other hand, when ore (Fe ₂ O ₃ ) having an oxidation degree of 1.5 is charged from the top of the furnace, the oxidation degree of the ore and the oxidation degree of the gas are along the straight line P _T -P _B (hereinafter referred to as operation line). Change. The fuel ratio of the blast furnace is determined by this linear gradient (C / Fe). When the operation of the blast furnace is ideally performed and the reduction equilibrium is reached, this straight line is in contact with the W point, and the fuel ratio takes the minimum value. However, in an actual blast furnace, the reduction of iron oxide deviates from equilibrium, so that the operation line does not pass through the W point, for example, passes through the P ₁ point. Here, the ratio (P ₀ -W) / (P ₀ -P ₁ ) of the lengths of the straight line P ₀ -W and the straight line P ₀ -P ₁ represents the degree of reduction equilibrium reached in the blast furnace, and is referred to as shaft efficiency. It is. Usually, the shaft efficiency of a blast furnace is about 0.90 to 0.95.
[0014]
When the pre-reduction ratio of the blast furnace charge is less than 30%, the oxidation degree of the blast furnace charge is lower than 1.5, so that _{PT ″} is substituted for _PT in FIG. As a result, the calorific value of the gas generated in the blast furnace increases, but in this case, the gradient of the operation line does not change, so the fuel ratio does not change in principle.
[0015]
On the other hand, when the preliminary reduction rate of the blast furnace charge exceeds 30%, the ordinate of the W point shifts to a W ′ point lower than 1.05. Assuming that the shaft efficiency is constant, the operation line passes through the point P _{1 '} where the shaft efficiency (P ₀ -P _1' / P ₀ -W ') is constant, and as a result, the gradient of the operation line becomes smaller and the fuel becomes lower. The ratio drops.
[0016]
That is, when the preliminary reduction rate of the blast furnace charging material is 30% or more (reduction stage in which FeO and some metallic iron exist), the fuel ratio of the blast furnace can be reduced according to the preliminary reduction rate, and as a result, the amount of gas generated in the blast furnace (= CO ₂ generation amount) can be reduced.
[0017]
By the way, performing the preliminary reduction of the sintered ore in this way means that a part of the reduction of the sintered ore, which has been conventionally reduced almost entirely in the blast furnace, is performed by the sintering machine. Here, the fuel ratio of the blast furnace charge decreases as described above when the pre-reduction rate of the charge exceeds 30%, but the sintering machine requires an extra carbon material required for ore reduction. In this case, in the sintering machine, iron ore can be reduced ideally until all the carbonaceous material becomes CO ₂ , whereas in the blast furnace, CO / CO ₂ has a constant distribution ratio, carbonaceous material for reducing the iron ore CO occurs always at a constant rate not the total amount of CO _2. For this reason, when reducing the same amount of iron ore, the reduction in the blast furnace is inevitably higher in the carbon material basic unit than the reduction in the sintering machine. Therefore, the amount of CO ₂ generated that is reduced by reducing the fuel ratio in the blast furnace becomes larger than the amount of CO ₂ generated that increases with the increase in the carbon dioxide basic unit of the sintering machine. That is, in order to reduce the amount of CO ₂ generated in the entire operation of the blast furnace, the sintered ore charged into the blast furnace is preliminarily reduced so that the preliminary reduction rate of the raw material charged in the blast furnace exceeds 30%. When using a material that has not been pre-reduced, the sintered ore may be pre-reduced at a reduction rate that results in a CO ₂ generation amount that is a predetermined amount or less less than the CO ₂ amount generated from the sintering machine and the blast furnace. . In this case, in order to make the CO ₂ reduction amount effective, it is preferable to reduce the CO ₂ amount by 10% or more. Note that when the fuel ratio in the blast furnace is reduced in this way, the amount of coke to be used is also reduced, so that the amount of CO ₂ generated in the coke furnace is actually reduced, and the CO ₂ reduction rate is further increased.
[0018]
Next, a specific example of blast furnace operation of the present invention will be described.
FIG. 3 is a diagram showing a specific example of the method of the present invention. Here, the pseudo particles produced by the pseudo particle production facility 100 are sintered by the downward suction type endless moving type sintering machine 200 and charged into the blast furnace 300.
[0019]
The pseudo particle manufacturing facility 100 stores a powdered iron ore hopper 1 that stores powdered iron ore, a return ore hopper 2 that stores returned ore, a medium hopper 3 that stores medium solvent, and powder coke for inner layers. An inner layer powder coke hopper 4, a primary drum mixer 5, a disk pelletizer 6, an outer layer powder coke hopper 7 for storing outer layer powder coke, and a secondary drum mixer 8 are provided. The fine iron ore supplied from the fine iron ore hopper 1 and the return ore supplied from the return ore hopper 2 constitute a sintered raw material.
[0020]
When manufacturing pseudo particles, a predetermined amount of fine iron ore and return mineral, medium solvent, and fine coke as a sintering raw material are cut out from each hopper, supplied to the primary drum mixer 5, and mixed while adding water. Subsequently, the mixed raw material is supplied to the disk pelletizer 6 and granulated while adding water. Thereby, the raw pellet of the state in which the powder coke was dispersed in the powdered ore is formed. Next, the raw pellets granulated by the disk pelletizer 6 are supplied to the secondary drum mixer 8 and mixed while adding water and the powder coke cut out from the powder coke hopper 7 for the outer layer. By this mixing, powder coke is coated on the surface of the raw pellets, and pseudo particles are produced. If granulation is sufficiently performed by the primary drum mixer 5 according to the raw material conditions, the granulation step by the disk pelletizer 6 may be omitted.
[0021]
The pseudo-particles thus produced have a two-layer structure of an inner layer 23 in which powder coke 22 is dispersed in the sintering raw material 21 and an outer layer 24 made of powder coke, as shown in FIG. The particle size is 2-20 mm.
[0022]
On the other hand, the downward suction type endless moving type sintering machine 200 has an endless moving type moving grate 11, and the pseudo particles are supplied onto the moving grate 11 by the charging system 10, and the layered bed 13a. Is to be formed. An ignition furnace 12 is provided in the movement path of the moving great 11, and the pseudo particles on the moving great 11 are ignited when passing through the ignition furnace 12, and the sintering of the bed 13a is started, and the sintering bed 13b. Is formed. A crusher (not shown) is provided on the exit side of the moving grate 11, and the sintered ore dropped from the moving grate 11 is crushed by the agglomerator and supplied to the conveyor 14 and supplied to the blast furnace 300.
[0023]
A plurality of wind boxes 15 are arranged immediately below the moving grate 11 along the traveling direction of the moving grate 11, and a vertical duct 16 is connected to each wind box 15. These vertical ducts 16 are connected to a main exhaust gas duct 17 disposed horizontally, and exhaust gas is discharged through the main exhaust gas duct 17. An exhaust gas circulation path 18 is provided in the main exhaust gas duct 17, and this exhaust gas circulation path 18 is connected to a gas supply unit 19 above the sintering bed 13 so that the exhaust gas is circulated during sintering. It has become. The exhaust gas is discharged from the chimney 32 by the main blower 31 from the main exhaust gas duct 17 through the electric dust collector 30 and the like.
[0024]
The pseudo particles are supplied onto the moving grate 11 of the lower suction type endless moving type sintering machine 200 via the charging system 10 and sintered. In sintering, a bed 13a of pseudo particles is formed on the moving great 11, and the surface of the bed 13a is ignited by an ignition furnace 12, and fired while sucking air downward through a wind box 15, thereby collecting a sintered ore. The sintered bed 13b which is a body is formed. After being sintered in this way, the sintered ore falls from the moving grate 11, and the sintered ore dropped by the crusher on the outlet side is crushed and supplied to the conveyor 14 and supplied to the blast furnace 300.
[0025]
In such a sintering process, it is preferable to circulate the exhaust gas through the exhaust gas circulation path 18 and the gas supply unit 19. By circulating the exhaust gas in this manner, the oxygen partial pressure in the system can be lowered, and sintering and reduction can be advanced while suppressing combustion of the carbonaceous material, thereby improving productivity.
[0026]
As described above, in the case of using the two-layer structure of the inner layer 23 in which the powder coke 22 is dispersed in the sintering raw material 21 and the outer layer 24 made of powder coke as the pseudo particles, the pseudo particles are sintered. The powder coke 22 dispersed in the sintering material 21 of the inner layer 23 mainly contributes to the reduction of the sintering material, and the powder coke of the outer layer 24 mainly contributes to the sintering. That is, the functions are separated between the inner layer coke and the outer layer coke, and reduction and sintering proceed simultaneously. According to the study results of the present inventors, the reduction reaction in the inner layer 23 proceeds mainly by a solid / solid reaction rather than a gas / solid reaction. It was found that depending on the particle size of 22, the smaller the particle size, the easier the reduction reaction occurs. More specifically, when coke having a particle diameter larger than 3 mm is used, the reduction reaction is suppressed and coke remains in the inner layer 23, but the coke is almost reduced by using the coke having a diameter of 3 mm or less. Was consumed. Accordingly, it is preferable to use a powder coke for the inner layer that is under 3 mm. In this case, the preliminary reduction rate of the sintered ore can be adjusted mainly by the amount of the powder coke in the inner layer.
[0027]
As the blast furnace charging raw material, other raw materials such as normal sintered ore can be used in addition to the pre-reduced partially reduced sintered ore.
[0028]
Next, the influence of the preliminary reduction rate of the raw material charged in the blast furnace when partially reduced sintered ore is used on the operation specifications of the blast furnace operation will be described. Here, pulverized coal (PCR): 200 kg / t, raceway theoretical temperature (TFT): 2100 ° C., shaft efficiency: 92%, heat loss: 250,000 kcal / t (constant).
[0029]
FIG. 5 shows the co-reduction ratio of the blast furnace charge with respect to coke ratio (CR), ore to coke weight ratio (O / C), air flow rate, oxygen excess rate, furnace top temperature, furnace top gas calorie, and pressure loss. It is a figure which shows the influence of. In addition, about each item, a continuous line is a case where normal coke is used, and a broken line is a case where highly reactive coke is used.
[0030]
Regarding CR, it makes up most of the fuel ratio described above, and it can be seen that the pre-reduction rate is reduced by 30% or more as described above. However, when the pre-reduction rate is 40% or more, the oxygen excess rate is less than 0.7, and the shaft efficiency is lowered and the air flow rate is forced to increase, so the CR reduction effect is reduced. As for O / C, when the pre-reduction rate exceeds 30%, the decrease in CR is larger than the decrease in ore accompanying the pre-reduction, so that the increase will go. The amount of blown air is greatly reduced because the amount of CO gas generation necessary for reduction can be reduced when the preliminary reduction rate is 30% or more. The oxygen excess rate is a ratio between the amount of oxygen being blown and the amount of oxygen that completely burns the pulverized coal, but decreases as the amount of blown air decreases due to the increase in the preliminary reduction rate. The temperature at the top of the furnace rises because the amount of charged material relatively decreases as the preliminary reduction rate increases. However, when the preliminary reduction rate is 30% or more, the amount of furnace top gas decreases at the same time, so that there is almost no change. The furnace top gas calorie increases with an increase in the preliminary reduction ratio up to a preliminary reduction ratio of 30%, but decreases with a reduction in the furnace top gas amount at a preliminary reduction ratio of 30% or more. The pressure loss ΔP is the value of the pressure loss from the top of the furnace to the stock line 10 m. However, when the pre-reduction rate is 30% or more, the pressure loss ΔP decreases with the reduction of the blowing amount.
[0031]
【Example】
Examples of the present invention will be described below.
The pseudo-particle production facility 100 and the downward suction type endless moving type sintering machine 200 shown in FIG. 3 produce and sinter pseudo-particles to produce partially reduced sintered ore with a pre-reduction ratio of 50%, which is then installed in the blast furnace. The blast furnace operation was performed so that the main raw material to be introduced was 80 mass% of partially reduced sintered ore, pellet mass%, and lump ore 10 mass%. The conditions at this time were a blowing temperature of 1200 ° C., a pulverized coal blowing ratio (PCR) of 200 kg / t, and a tuyere tip combustion temperature of 200 ° C. The amount of CO ₂ discharged in the coke oven, sintering machine and blast furnace at this time was determined. On the other hand, substantially coke oven in the case of blast furnace operation under the same conditions except for using sinter that is not pre-reduced, the sintering machine and CO ₂ emissions in the blast furnace (discharge amount of carbon CO ₂ for comparison (Converted value) was also obtained. These CO ₂ emissions are compared and shown in FIG.
[0032]
As shown in FIG. 6, in the case of the present invention example using the partially reduced sintered ore, the CO ₂ emission amount in the sintering machine was 2.2 times that of the comparative example not using the partially reduced sintered ore. but 26% in the blast furnace, since became less 15% CO ₂ emissions coke oven, coke oven, a sintering machine and blast the total could be reduced 12% CO _2. Since the absolute value of the difference in CO ₂ emission from the coke oven is small, the CO ₂ reduction amount in the sintering machine and the blast furnace was approximately 12% by using the partially reduced sintered ore. In this way, by using partially reduced sintered ore with a predetermined preliminary reduction rate, it is possible to achieve a 12% reduction in CO ₂ in the sintering machine and blast furnace than when using sintered ore that has not been subjected to preliminary reduction. Was confirmed.
[0033]
【The invention's effect】
According to the present invention, blast furnace operation method capable of effectively reducing the CO ₂ emissions of the sintering machine and blast furnace total is provided. Therefore, the present invention is extremely valuable from the viewpoint of preventing global warming.
[Brief description of the drawings]
FIG. 1 is a diagram showing a gas temperature distribution in a blast furnace.
FIG. 2 is a list diagram showing blast furnace operation when partially reduced sintered ore is used.
FIG. 3 is a diagram showing a specific example of the method of the present invention.
FIG. 4 is a cross-sectional view showing pseudo particles having a two-layer structure for producing partially reduced sintered ore.
FIG. 5 shows the effect of blast furnace charge on coke ratio (CR), ore and coke weight ratio (O / C), blast volume, oxygen excess rate, furnace top temperature, furnace top gas calorie, and pressure loss in a blast furnace. FIG.
FIG. 6 is a diagram showing the effect of the present invention.
[Explanation of symbols]
1 …… Powder iron ore hopper 2 …… Returning hopper 3 …… Medium solvent hopper 4 …… Inner layer coke hopper 5 …… Primary drum mixer 6 …… Disc pelletizer 7 …… Outer layer coke hopper 8 …… 2 Next drum mixer 10 ... charging system 11 ... moving great 12 ... ignition furnace 13a ... bed 13b ... sintering bed 18 ... exhaust gas circulation path 100 ... pseudo particle production facility 200 ... bottom suction type endless moving type Sintering machine 300 ... Blast furnace

Claims (2)

Sintering raw material containing fine iron ore and carbonaceous material with a sintering machine to produce sintered ore, and charging blast furnace containing raw material containing this sintered ore into the blast furnace and operating the blast furnace A blast furnace operating method comprising:
The pre-reduction rate of the sintered ore is pre-reduced as a sintered ore charged in the blast furnace in a sintering machine and a blast furnace so that the pre-reduction rate of the raw material charged in the blast furnace is 30% or more. A method for operating a blast furnace, characterized in that control is performed so that a CO ₂ generation amount is a predetermined amount or more less than a CO ₂ amount generated when a non-existing one is used.   The blast furnace operating method according to claim 1, wherein the predetermined amount is 10%.

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