JP2006207009A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace, which blows a liquid or gaseous ancillary reducing material such as fuel oil and a natural gas, which has a high heating value and does not contain ash, into the blast furnace together with a solid reducing material, but prevents the degradation of air permeability, and consequently takes out the maximum effect of charged hydrogen. <P>SOLUTION: The method for operating the blast furnace while blowing the gaseous or liquid reducing material as the ancillary reducing material together with the solid reducing material from a tuyere includes blowing the gaseous reducing material or liquid reducing material having a ratio H/C of 1.5 or larger simultaneously with the solid reducing material, while adjusting the quantity to be blown of the solid reducing material and/or the gaseous reducing material or the liquid reducing material so that a ratio of H<SB>2</SB>/CO in the Bosch gas can be 0.22 or larger. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a blast furnace operating method in which a solid reducing material and a gas reducing material or a liquid reducing material are blown as auxiliary reducing materials from a blast furnace tuyere.

Coke used as a reducing material in blast furnaces that produce pig iron generally requires expensive strong caking coal as a raw material, and also costs for the construction, operation, repair, etc. of the coke oven that is its production equipment. Expensive. For this reason, reduction of the pig iron manufacturing cost by reduction of the usage-amount of coke in a blast furnace is desired.
In addition, it is an urgent need to reduce the amount of coke used in the blast furnace from the viewpoint of suppressing the generation of CO ₂ in the ironmaking process and contributing to the preservation of the global environment.

As a technique for reducing the amount of coke used and suppressing CO ₂ generation in the iron making process, a technique for blowing a reducing material (for example, pulverized coal, synthetic resin material, etc.) containing a large amount of hydrogen from the tuyere is known. . And in order to improve the combustibility of solid reducing materials, such as pulverized coal and a synthetic resin material, the technique in which gaseous reducing materials, such as natural gas and city gas, are simultaneously blown into the solid reducing material is proposed (for example, patent documents). 1).
Japanese Patent Publication No. 1-289847

As described above, it is considered that reducing material containing a large amount of hydrogen is blown from the tuyere to be effective in reducing CO ₂ generation in the ironmaking process. The following effects can be given as other effects.
(1) Reducing pressure loss in the furnace due to low density and low viscosity can be achieved.
(2) The shaft efficiency can be increased and the reducing material ratio can be decreased by increasing the reduction speed. Moreover, since the amount of Bosch gas can be reduced by reducing the reducing material ratio, the pressure loss can be reduced.
(3) It is possible to improve the meltability of the ore in the cohesive zone and to reduce the pressure loss associated therewith.
(4) The coke pulverization can be reduced by reducing the solros load, and the powder rate of the packed portion in the lower part of the furnace can be reduced, and the pressure loss associated therewith can be reduced.
Thus, it can be pointed out that hydrogen charging is effective for reducing the pressure loss in the furnace based on various reasons.

As described above, since hydrogen injection is effective for reducing the pressure loss in the furnace, the pressure loss in the furnace is reduced by blowing pulverized coal, which is an example of a reducing material containing a large amount of hydrogen, or a synthetic resin material as an auxiliary reducing material. It seems to be able to reduce.
However, solid reducing materials such as pulverized coal and synthetic resin materials have a low calorific value, and ash components tend to accumulate in the back of the raceway. It is difficult to increase the replacement ratio with coke to 1.0 or more due to an increase in furnace pressure loss.
Therefore, increasing the blowing amount of the solid reducing material is effective for reducing the coke ratio, but the reducing material ratio is not only increased, but also has an adverse effect on the suppression of CO ₂ generation and the demand for increased production. Become.

This point will be described more specifically. For example, when pulverized coal containing about 5 to 7% of hydrogen is blown, the amount of hydrogen input can be increased as the amount of blown is increased. Here, the hydrogen (H ₂ ) concentration in the entire reducing gas (CO + H ₂ ) in the Bosch gas is represented by H ₂ / CO, and this is used as an index.
As can be seen from FIG. 5, which graphically shows the relationship between the pulverized coal ratio and H ₂ / CO, as the pulverized coal ratio increases, H ₂ / CO increases linearly, so the pressure loss decreases as an effect of hydrogen input. It is predicted that such effects will be demonstrated.
However, in actuality, this index H ₂ / CO and blast furnace lower ventilation resistance index K (hereinafter referred to as “furnace lower K value”, K = (P _blast ² -P ² ) / V ^1.7 where P _blast FIG. 6 is a graph showing the relationship between: blowing pressure (kg / cm ² ), P: furnace wall static pressure (kg / cm ² ) just above the Bosch part, and V: Bosch gas amount (Nm ³ / t)). As can be seen, contrary to the above prediction, the K value increased with an increase in the amount of hydrogen input, and the opposite effect to that expected by hydrogen input was obtained for the air permeability.
This is thought to be because the accumulation of ash derived from pulverized coal and the increase in pressure loss due to the generation and accumulation of unburned char exceeded the effect of pressure loss mitigation due to hydrogen input.
Therefore, in order to enjoy the above-described effects of hydrogen input, it is not sufficient to blow the solid reducing material alone, and further technological development such as optimization of the hydrogen input method and amount is necessary.

In this respect, in Patent Document 1, since a gas reducing material such as natural gas, which has a high calorific value and does not contain ash, is blown together with the solid reducing material, a certain effect is expected to prevent deterioration of air permeability. I think it can be done.
However, in Patent Document 1, if the gas reducing material is blown in under any condition, hydrogen is charged rather than the accumulation of ash derived from the solid reducing material such as pulverized coal and the increase in pressure loss due to the generation and accumulation of unburned char. There is no disclosure or suggestion as to whether the effect of hydrogen input can be obtained by exceeding the effect of reducing the pressure loss due to.

Therefore, the subject of the present invention is that when a reducing material containing a large amount of hydrogen is blown from the tuyere as an auxiliary reducing material, in order to achieve both the maintenance of air permeability and the reduction of the reducing material ratio, any auxiliary reducing material under what conditions It is to indicate whether or not to blow in.
The present invention has been made to solve such a problem, and in the case where a liquid or gaseous auxiliary reducing material such as heavy oil or natural gas, which has a high calorific value and does not contain ash, is blown together with the solid reducing material. An object of the present invention is to provide a method for operating a blast furnace capable of maximizing the effect of hydrogen input while preventing deterioration of air permeability.

In order to solve the above-mentioned problems, the inventors conducted a blow test in an actual blast furnace (a blast furnace having a bell-less charging device with an internal volume of 3224 m ³ ), and conducted extensive studies. In this test, Bosch was injected by changing natural gas from 0 to 100 kg / tp in increments of 20 kg / tp in three cases where the amount of pulverized coal injection was constant at 50 kg / tp, 100 kg / tp, and 150 kg / tp. changing the H ₂ / CO in the gas, is that to investigate the relationship between the furnace bottom K value and the H ₂ / CO.

FIG. 1 is a graph showing the results of this investigation. The vertical axis represents the furnace bottom K value, and the horizontal axis represents H ₂ / CO.
As shown in FIG. 1, regardless of the amount of pulverized coal injected, if the H ₂ / CO in the Bosch gas is increased to 0.22 or more by natural gas injection, the lower K value of the furnace clearly decreases. . These are judged to be the result of having enjoyed the above-described effects of hydrogen input by introducing hydrogen derived from a reducing material not containing ash.

  In the above experiment, natural gas is exemplified as a gas reducing material to be blown together with the solid reducing material. However, in order to obtain the above effect, a gas or liquid reduction having a high calorific value and a large amount of hydrogen containing no ash Any material can be used.

In general, examples of the gas reducing material or the liquid reducing material include those shown below.
Methane (CH ₄ , H / C (molar ratio of hydrogen to carbon in average composition) = 4.0), ethane (C ₂ H ₆ , H / C = 3.0), propane (C ₃ H ₈ H / C = 2.7), butane (C ₄ H ₁₀ , H / C = 2.5), pentane (C ₅ H ₁₂ , H / C = 2.4), ethylene (C ₂ H ₄ , H /C=2.0), propylene (C ₃ H ₆ , H / C = 2.0), dimethyl ether ((CH ₃ ) ₂ O, H / C = 3.0), benzene (C ₆ H ₆ , H /C=1.0), toluene (C ₆ H ₅ CH ₃ , H / C = 1.33), and natural gas (LNG) which is a mixture of methane, ethylene, propane, etc. (H / C is 3. 7 to 4.0), coke oven gas (COG) mainly composed of methane and hydrogen (H / C is about 5.9), crude oil (H / C is about 1.87), kerosene (H / C is About 1.97), light oil (H / C is about 1.84), heavy oil (1.55 to 1.75), triol (C ₇ H ₈ , H / C = 1.1), naphthalene (C ₇ H ₈ , H / C = 1) .1).

Among these gas reducing materials or liquid reducing materials, gas reducing materials (benzene, toluene, etc.) or liquid reducing materials (triol, naphthalene, etc.) with H / C of 1.5 or less are thermally decomposed and solidified immediately after blowing. Form C (soot) is likely to occur, and there is a problem in effectiveness as a heat source.
Accordingly, it is desirable that the gas reducing material and the liquid reducing material have H / C of 1.5 or more, and the above-described ethane, methane, or the like may be used alone or in combination.
Note that COG, LNG, and the like in which various gases are mixed in advance also meet this condition.
Specifically, from the viewpoint of easy availability, natural gas is particularly preferred as the gas reducing material, and heavy oil is particularly preferred as the liquid reducing material.
This invention is made | formed based on this knowledge, and has the structure of the following (1)-(3) specifically ,.

(1) The blast furnace operating method of the present invention is a blast furnace operating method in which a solid reducing material and a gas reducing material and / or a liquid reducing material are blown from the tuyere as an auxiliary reducing material. The above liquid reducing material or gas reducing material is simultaneously blown, and the amount of blowing of the solid reducing material and / or gas reducing material or liquid reducing material is adjusted so that H ₂ / CO in the Bosch gas is 0.22 or more. It is characterized by doing.

The method of setting H ₂ / CO to 0.22 or more is not particularly limited. For example, the blowing of the solid reducing material and the gas reducing material based on the estimated value of the gas concentration in the Bosch gas by the mass balance calculation. The injection amount of the liquid or gas reducing material may be adjusted appropriately while determining the injection amount or monitoring H ₂ / CO in the Bosch gas by actual measurement.

(2) Further, another blast furnace operating method of the present invention is characterized in that heavy oil is used as the liquid reducing material shown in (1) and natural gas is used as the gas reducing material.

(3) Moreover, pulverized coal and / or a synthetic resin material is used as the solid reducing material in the above (1) or (2).

In the present invention, in a blast furnace operating method in which a solid reducing material and a gas reducing material or a liquid reducing material are blown from the tuyere as auxiliary reducing materials, the liquid reducing material or the gas reducing material having an H / C of 1.5 or more together with the solid reducing material. blowing timber simultaneously, and since H ₂ / CO in the Bosch gas is to adjust the blowing amount of the solid reducing material and / or gaseous reducing agent or liquid reducing agent so that the 0.22 or more, CO ₂ Can be significantly reduced, and the reducing material ratio can be reduced while suppressing an increase in pressure loss in the furnace.

In the present invention, paying attention to H ₂ / CO in the Bosch gas, by making the specific value 0.22 or more, accumulation of ash derived from a solid reducing material such as pulverized coal or unburned char Although it has been shown that the pressure loss mitigation effect by hydrogen injection can be surpassed by the pressure loss increase effect due to generation and accumulation, this has great significance. This is because, by indicating such an index, a specific example in which H ₂ / CO in the Bosch gas is 0.22 or more in the conventional case where there is a limit in blowing the solid reducing material due to an increase in pressure loss. This is because, together with the numerical value, it was shown that the increase in pressure loss can be alleviated sharply with this numerical value as a boundary, thereby making it possible to make the operating conditions more flexible in blast furnace operation.

FIG. 2 is an explanatory view of the outline of a blast furnace having a bell-less charging device used for carrying out the blast furnace operating method according to the present embodiment and its peripheral equipment.
As shown in FIG. 2, the blast furnace used in the present embodiment and its peripheral equipment include a blast furnace 1 having an internal volume of 3223 m ³ and a blower pipe 2 for sending hot air to the blast furnace 1. A pulverized coal blowing lance 3, a synthetic resin material blowing lance 4, and a gas reducing material blowing lance 5 are installed.

In the blast furnace operating method of the present embodiment, pulverized coal is blown from the tuyere as a solid reducing material that is an auxiliary reducing material, and natural gas is used as a gaseous reducing material that also has an H / C of 1.5 or more as an auxiliary reducing material. Infuse.
When the auxiliary reducing material is blown, the amount of blowing the auxiliary reducing material is adjusted so that H ₂ / CO in the Bosch gas is 0.22 or more.

As a method for adjusting the amount of blowing in the auxiliary reducing material, for example, the following is performed.
When pulverized coal and natural gas are injected, the chemical composition (C, O, H, N, etc.) of pulverized coal and natural gas, the amount of these injections, and the total oxygen intensity in the blown air are calculated. Estimated values of the pulverized coal injection ratio and the natural gas injection ratio satisfying the condition of H ₂ / CO of 0.22 or more are obtained in advance.

FIG. 3 is a graph showing conditions for satisfying a predetermined value of H ₂ / CO in the Bosch gas when the oxygen enrichment rate is constant at 3%, and the vertical axis represents the natural gas blowing ratio. The horizontal axis represents the pulverized coal injection ratio. In FIG. 3, the boundary line of the region where H ₂ / CO in the Bosch gas is 0.22 or more is indicated by a bold line, and the other region where H ₂ / CO is 0.2, 0.3, or 0.4. The boundary line is indicated by a broken line.
A similar diagram can be obtained when the oxygen enrichment rates are different.

According to FIG. 3, in order to make H ₂ / CO in the Bosch gas 0.22 or more, for example, when the pulverized coal injection ratio is 50 kg / tp, the natural gas injection ratio is about 24 kg / tp or more. When the pulverized coal ratio is 100 kg / tp, the natural gas injection ratio is about 15 kg / tp or more. When the pulverized coal ratio is 150 kg / tp, the natural gas injection ratio is about 5 kg / tp or more. .
However, even if the natural gas injection ratio is determined based on FIG. 3 above, the natural gas is obtained by directly sampling the Bosch gas during operation and grasping the concentrations of CO, H ₂ , H ₂ and N ₂ in the gas. The gas blowing ratio may be further adjusted.

As described above, by setting the natural gas injection ratio so that H ₂ / CO in the Bosch gas is 0.22 or more, as shown in FIG. The K value decreases and the ventilation resistance in the furnace can be relaxed. Correspondingly, the reducing material ratio is easily lowered.

In the above example, as a method of H ₂ / CO in the Bosch gas to 0.22 or more, pulverized coal blowing ratio H ₂ / CO in the Bosch gas satisfies 0.22 or more conditions and natural An example is shown in which an estimated value of the gas injection ratio is obtained in advance, and natural gas is injected based on the estimated value obtained in advance.
However, the present invention is not limited to this. For example, even if a basic value is not obtained in advance by calculation, the Bosch gas is directly sampled in actual operation to obtain CO, H ₂ , H ₂ , N in the gas. While grasping the concentration of ₂ , the natural gas blowing ratio may be adjusted.
As a method for adjusting H ₂ / CO in the Bosch gas to 0.22 or more, not only the natural gas blowing ratio but also the blowing ratio of a solid reducing material such as pulverized coal is adjusted. Also good.

  In the above embodiment, an example in which only pulverized coal is blown as a solid reducing material has been described. However, the present invention is not limited to this, and pulverized coal and a synthetic resin material may be simultaneously blown. Alternatively, the synthetic resin may be blown alone.

Hereinafter, detailed explanation of the effect of adjusting the H ₂ / CO in the Bosch gas 0.22 or more.
For three cases with pulverized coal injection ratios of 50 kg / tp, 100 kg / tp, and 150 kg / tp, the H ₂ / CO in the Bosch gas is changed by changing the natural gas injection ratio every 20 kg / tp. The relationship between the reducing material ratio and H ₂ / CO at that time was determined.
FIG. 4 is a graph showing the relationship between the reducing material ratio and H ₂ / CO in Bosch gas, where the vertical axis shows the reducing material ratio and the horizontal axis shows H ₂ / CO in Bosch gas.

As shown in FIG. 4, even when natural gas is blown in, if the H ₂ / CO in the Bosch gas is less than 0.22, the effect of reducing the reducing agent ratio is hardly seen in any of the above three cases.
However, when the natural gas blowing ratio is increased and the H ₂ / CO in the Bosch gas is set to 0.22 or more, the effect of reducing the reducing material ratio is remarkable in any of the above three cases.

For example, in the case of a pulverized coal injection ratio of 50 kg / tp, the reducing material ratio is 493 kg / tp when H ₂ / CO in Bosch gas is 0.29, and H ₂ / CO in Bosch gas is Compared to 498 kg / tp when the value is less than 0.22, it is reduced by 5 kg / tp.
In the case of the pulverized coal injection ratio of 100 kg / tp, the reducing material ratio is 499 kg / tp when H ₂ / CO in the Bosch gas is 0.32, and the H ₂ / CO in the Bosch gas is Compared to 505 kg / tp when the value is less than 0.22, 6 kg / tp can be reduced.
Furthermore, in the case of the pulverized coal injection ratio of 150 kg / tp, the reducing material ratio when the H ₂ / CO in the Bosch gas is 0.35 is 505 kg / tp, and the H ₂ / CO in the Bosch gas is Compared to 512 kg / tp when the value is less than 0.22, it is reduced by 7 kg / tp.

As described above, by setting H ₂ / CO in the Bosch gas to 0.22 or more by blowing natural gas, the air permeability is improved, and a reduction in the reducing material ratio can be realized as an effect of hydrogen input.

It is a graph for demonstrating the basis of this invention. It is explanatory drawing of the blast furnace and its peripheral equipment which implements this invention. It is explanatory drawing explaining the adjustment method of the blowing ratio of the gas reducing material in one embodiment of this invention. It is a graph for demonstrating the effect of the Example of this invention. Is a graph for explaining a problem of the present invention, is a graph showing the relationship between the concentration ratio of H ₂ and CO in the pulverized coal blow ratio and Bosch gas (H ₂ / CO). Is a graph for explaining a problem of the present invention, is a graph showing the relationship between the furnace bottom K value of H ₂ / CO and actual furnace.

Explanation of symbols

    1 Blast furnace, 2 air duct, 3 pulverized coal injection lance, 4 synthetic resin material injection lance, 5 gas reducing material injection lance.

Claims (3)

In a blast furnace operation method in which a solid reducing material and a gas reducing material and / or a liquid reducing material are blown as auxiliary reducing materials from a tuyere, a liquid reducing material or a gas reducing material having an H / C of 1.5 or more is simultaneously added together with the solid reducing material. A method for operating a blast furnace, characterized in that the blowing amount of the solid reducing material and / or the gas reducing material or the liquid reducing material is adjusted so that H ₂ / CO in the Bosch gas is 0.22 or more. The blast furnace operating method according to claim 1, wherein heavy oil is used as the liquid reducing material and natural gas is used as the gas reducing material. The blast furnace operating method according to claim 1 or 2, wherein pulverized coal and / or a synthetic resin material is used as the solid reducing material.

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