JP2000204405A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and stably form a titanium bear in a brick damaged position of a furnace hearth part in a blast furnace. SOLUTION: The titanium bear is formed in the brick damaged position of the furnace hearth part by blowing mixed powder containing titanium oxide, metallic aluminum and carbonaceous material from selected one or plural tuyeres among many tuyeres disposed at the furnace hearth part in the blast furnace. Since the titanium bear is quickly and stably formed in the brick damaged position of the furnace hearth part, a quick action can be taken to the heating up caused by the brick damage of the furnace hearth part. Since the titanium quantity forming the titanium bear can be saved, the prolongation of the service life of the brick of the furnace hearth part can be achieved at a low cost and the trouble in the iron and slag tapping operation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace, which suppresses wear of bricks in a hearth of a blast furnace and prolongs the life of the blast furnace body.

[0002]

2. Description of the Related Art Reduction of pig iron production cost in a blast furnace is an important theme in the field of ironmaking, such as the use of inexpensive raw materials and fuel, such as pulverized coal injection from tuyeres, and the reduction of refractory unit consumption. Technology development is taking place. In particular, extending the life of the furnace to reduce the frequency of refurbishment of the blast furnace, which is very expensive, is very important for cost reduction.

[0003] The furnace body of a blast furnace is composed of a steel shell, a cooling plate, a refractory, and the like provided inside thereof, but is damaged by wear and melting due to a high-temperature substance present therein during operation. . Due to the recent advances in blast furnace furnace body repair technology, the furnace body above the tuyere has its scale reduced in the furnace during a calm period when the operation of the blast furnace temporarily stops, and the stacking surface of the charging section The intermediate repair can be performed by lowering the furnace below the furnace body repair site. However, in the case of the hearth below the tuyere, it is difficult to make intermediate repairs due to the presence of hot metal slag.
For this reason, the most important factor that determines the life of the furnace body is the damage state of the hearth, and at present, the hearth brick determines the life of the blast furnace.

[0004] In order to prevent the hearth brick from being worn, cooling of the hearth and use of carbon brick having excellent corrosion resistance have been widely performed. In addition, since the thermal stress that occurs when the heat level in the hearth changes rapidly, such as when the blast furnace is turned on or when there is a long-term wind break, the hearth brick can also be degraded. Has also been made. In addition, during normal operation of the blast furnace, the erosion status of the hearth brick cannot be directly measured.Therefore, the temperature of each part of the hearth is measured by a thermometer embedded in the hearth brick forming the hearth and the hearth side wall. Is measured, and the remaining brick thickness is estimated from the heat transfer calculation. Since the information on the remaining brick thickness obtained in this manner is information including the pig iron solidified layer, the accurate remaining brick thickness is not always shown. However, the material and shape of the hearth brick can be changed only when the blast furnace is turned on, and even if it is found that the remaining brick thickness has decreased by temperature measurement during operation, brick replacement and restoration etc. Impossible.

[0005] In a dismantling survey accompanying the blast furnace renovation, a concentrated layer of a titanium compound, so-called titanium bare, has been observed in pig iron in contact with the hearth brick. Titanium bear is generally TiN
And TiC with melting points of 2950 ° C and 3150 ° C.
Because of the extremely high temperature of ℃, if the titanium bare can be actively generated during the blast furnace operation, the area in contact with the hearth brick can be maintained in a solidified state, preventing erosion of the hearth brick It is possible. As a method of forming a titanium bear on the hearth, a technique of charging a sintered ore containing a titanium source such as iron sand from the blast furnace top is used. However, in this case, titanium dissolves not only in the area where the brick damage is large, but also in the hot metal
The fluidity of the hot metal decreases, and the amount of hot metal slag generated in the furnace and the amount of hot metal slag discharged from the taphole are unbalanced. Become.

Therefore, a technique has been developed in which Ti is efficiently supplied only to a severely damaged portion of the hearth to generate a titanium bare. For example, in Japanese Unexamined Patent Publication No. 9-227910, a tracer is placed from a tuyere near the center between two tap holes separated by a central angle of 90 ° or more from each other with a furnace bottom side wall having a locally raised temperature interposed therebetween. The hot metal flow in the hearth is estimated from the difference in the response time of the tracer concentration from the tap hole, and it is determined that brick wear in the area where the hot metal flow rate is increasing is progressing. , Powder of Ti-containing iron raw material
A technique for forming a titanium bare by blowing as a Ti source is disclosed. Also, in Japanese Patent Application Laid-Open No. 4-297511, a metal such as Co or Ni, or a metal oxide is blown in consideration of the fact that the fluidity of the hot metal is deteriorated due to dissolution of Ti, and the efficiency of the hot metal is changed from the concentration change in the hot metal. Discloses a technique of injecting a Ti source into a gas.

[0007]

However, when a Ti source is blown from the tuyere of a blast furnace as in the above-mentioned prior art, there is a problem that the yield of Ti transferred to hot metal is low. Therefore, it is necessary to blow a large amount of Ti source from the tuyere, and as a result, there is a problem that not only the damaged portion of the brick but also the titanium concentrated layer spreads over a wide range of the blown tuyere. Further, an increase in the blowing amount of the Ti source leads to an increase in cost.

The present invention solves these problems of the prior art, and directly blows powder of a simple mixture of titanium carbide and titanium nitride, which are constituent materials of titanium bare, or powders of titanium metal. The titanium oxide is reduced in the raceway (coke combustion area) formed at the tip of the tuyere by blowing into it to form a titanium bear on the hearth as carbide or nitride, thereby suppressing damage to the hearth. The purpose is to extend the life of hearth brick.

[0009]

According to a first aspect of the present invention, there is provided a blast furnace in which one or more selected tuyeres are selected from tuyeres disposed on a hearth portion of a blast furnace. A method of operating a blast furnace, comprising blowing a titanium carbide powder, a titanium nitride powder or a mixture powder of a titanium carbide and a titanium nitride from a blast furnace.

According to a second aspect of the present invention, there is provided a blast furnace characterized in that metallic titanium powder is blown from one or a plurality of selected tuyeres among tuyeres disposed on a hearth of a blast furnace. It is an operation method. According to the third aspect of the present invention, a powder mixture containing titanium oxide and metallic aluminum is blown from one or a plurality of selected tuyeres among a large number of tuyeres arranged in a hearth of a blast furnace. This is a method for operating a blast furnace, which is characterized in that:

In a mixture containing titanium oxide and metal aluminum, it is preferable that the weight ratio of metal aluminum to titanium oxide is about 1 to 2 for metal aluminum to 1 for titanium oxide. By setting the content within this range, the reaction between the metal aluminum and the titanium oxide is performed without excess or deficiency. It is also effective to blow a mixture obtained by further adding a carbon material to a mixed powder containing metal aluminum and titanium oxide. The carbon material added has the effect of increasing the amount of carbon in the reaction region between metallic aluminum and titanium oxide, and has the effect of promoting the formation of TiC. Moreover, the carbonaceous material that has not contributed to the reaction is consumed as fuel, so that it is used unnecessarily. Therefore, the mixing ratio of the carbon material does not need to be particularly specified.

Further, as the above-mentioned titanium oxide, iron sand, illuminite and rutile can be suitably used. In these cases, it is preferable that the weight of TiO ₂ contained in iron sand, illuminite, and rutile is in the above-mentioned ratio with respect to metallic aluminum.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a mechanism for forming titanium bare in a hearth of a blast furnace, a mechanism in which Ti in hot metal is crystallized as TiC and TiN, and a mechanism in which TiO ₂ and Ti ₂ O ₃ in slag are reduced by Si and the like. A mechanism has been proposed that transfers to hot metal to generate TiC and TiN. Slow the hot metal flow either case, Ti slowly TiC in hot metal when the temperature and the N ₂ partial pressure by a change in the operating conditions change, crystallized as a solid solution of TiN.

However, since the viscosity of the hot metal increases linearly with the increase of the Ti concentration in the hot metal, there is a possibility of causing a tapping slag trouble or the like. Therefore, in the present invention, since TiC and TiN are directly supplied to the hearth without dissolving Ti in the hot metal, TiC and TiN are supplied from one or more selected tuyeres.
Powder, TiN powder or a mixture thereof. This makes it possible to efficiently repair only the damaged part of the hearth without deteriorating the tapping residue.

Since TiC and TiN are expensive, TiC and TiN
Alternatively, metal Ti may be blown. Metal Ti blown from the tuyere can generate TiC and TiN by reacting with nitrogen or carbon dioxide in the air in the hot raceway, forming a titanium bear and repairing the damaged part of the hearth it can. In addition, directly from cheaper titanium oxide
TiC and TiN may be generated. However, Ti has a very strong affinity for oxygen and forms a stable oxide, and it is difficult to reduce titanium oxide such as iron sand, illuminite, rutile, and the like by a normal reaction with a reducing agent. Therefore, the present inventors have studied reduction of titanium oxide by a solid-gas reaction. As a result, they have found that titanium oxide can be reduced by Al at a high temperature of 2000 ° C. or higher.

In the present invention, a powder mixture of titanium oxide and metal Al or further carbon material is blown from one or more selected tuyeres. This makes it possible to extend the life of the furnace body using the titanium bear while minimizing an increase in hot metal cost.
The selection of the tuyere for injecting the Ti source can be performed, for example, by measuring the temperature of the furnace bottom with a thermometer embedded in the furnace bottom or the bottom wall of the furnace, estimating the remaining brick thickness from heat transfer calculation, and measuring the remaining brick thickness at other locations. The tuyere provided in the information of the thinner part is selected. In addition, the tuyere selection criterion may be such that metal powder such as Co or Ni is blown from the tuyere, and the upper part of the brick wear site estimated from the response time of the metal concentration in the hot metal.

The reaction between titanium oxide and metal Al is represented by the following chemical formula (1). 4Al + TiO ₂ = Ti + 2Al ₂ O, ΔG = 552.1-0.2435T (kJ / mol) (1) Assuming that solid metals and oxides are pure substances, the parallel partial pressure of Al ₂ O is 1800 ° C or more. Is about 1 atm. The generated Al ₂ O is constantly updated by blowing air, and the reduction in titanium oxide proceeds by a reaction in the raceway. Although there is a concern that the reaction time is short, the injected metal Al and titanium oxide stay on the inner surface (bird's nest) of the raceway, and there is no problem because the reaction occurs there.

The above estimation of the reaction was confirmed by experiments using a test furnace. Powders A to E shown in Table 1 were blown from tuyeres provided at the lower part of a vertical test furnace (one tuyere, furnace inner diameter 0.6 m) in which coke and sinter were alternately filled in layers. A comparative test was conducted to analyze the metal formed in the inside. Powder A is titanium oxide, powder B is a mixed powder of titanium oxide and metal Al,
Powder C is a powder mixture of titanium oxide and aluminum slag, powder D is a powder mixture of titanium oxide, metal Al and pulverized coal, and powder E
Shows a case where a mixed powder of titanium oxide, aluminum slag and pulverized coal is blown. Illuminite was used as titanium oxide. Aluminum slag is slag powder mainly composed of metallic aluminum generated in an aluminum refining furnace.

[0019]

[Table 1]

The experimental conditions were as follows: air flow from tuyere 90Nm ³ / hr,
The blowing temperature was 1100 ° C., the oxygen enrichment rate was 4%, the blowing humidity was 18 g / Nm ³ , and the pulverized coal blowing rate was 300 g / min. Titanium oxide calculated from the Ti concentration in pig iron accumulated in the hearth is a titanium compound (Ti
N, TiC) are shown in Table 1. As shown in Table 1, when illuminite containing titanium oxide as a main component is mixed with a substance containing metal Al or a carbonaceous material such as pulverized coal from the tuyere and blown, titanium oxide is reduced by Al. And reacts with C in the carbonaceous material to produce TiC,
Alternatively, it was found that TiN was formed by reacting with N _{2 being} blown. In this case, the substance containing metal Al as a component refers to metal aluminum, slag containing metal aluminum, and the like. Since the generated titanium compounds such as TiN and TiC are very stable, they fall into the molten iron pool at the lower part of the furnace without being altered by the reaction, and form titanium bears.

Since the partial pressure of O ₂ in the raceway formed at the tuyere tip is high, a part of the reduced Ti is reoxidized. However, the yield of titanium compounds is significantly higher than that of slag in the hearth by blowing in titanium oxide alone or by reduction and crystallization reactions in hot metal. It is a source of titanium bare at Also,
By using a titanium compound in the raceway, an increase in the concentration of Ti dissolved in the hot metal can be prevented, and there is no need to worry about deterioration in the fluidity of the hot metal due to an increase in the amount of titanium oxide blown.

Further, the same effect as described above can be obtained by blowing titanium carbide, titanium nitride or a mixture of titanium carbide and titanium nitride from the tuyere, or by blowing metal titanium powder to generate nitride or carbide. Can be obtained. However, these methods increase the cost of the blowing material.

[0023]

[Example] Using a blast furnace with an inner volume of 4500 m ³ and 40 tuyeres,
When the bottom wall temperature measured with a thermocouple buried 2 m below the tuyere in normal blast furnace operation exceeded 200 ° C, three tuyeres located above the part where the bottom temperature increased were selected. The powder was blown by the method of the present invention and the illuminite alone was blown by the conventional method. The operating conditions are as usual, the air temperature from the tuyere is 1050-1100 ° C, and the oxygen enrichment rate is 1
%, Dezukuhi 1.7t / dm ^3, the coke ratio 400kg / tp, pulverized coal ratio
It is 108 kg / tp. The blast furnace has four tap holes in the direction of ± 22.5 degrees from east and west.

In the conventional method, the illuminite powder is introduced into the tuyere 1
It was blown at a rate of 530 kg / hr per book. In the method of the present invention, the illuminite 1 is adjusted so that the titanium oxide equivalent is the same.
Inventive method-1 in which powder mixed at a weight ratio of Al 1.35 to the tuyere is blown at a rate of 1250 kg / hr per tuyere, and Illuminite 1 is mixed at a weight ratio of Al 1.35 and pulverized coal 0.22 Inventive method-2 in which the powder thus obtained was blown at a rate of 1360 kg / hr per tuyere. Further, in the same manner, in order to have the same titanium equivalent, Al1.35 and pulverized coal
1980kg / h of powder mixed with 0.22 weight ratio per tuyere
Inventive method-3, which blows at a rate of r, and Ti-4 powder, which blows at a rate of 400 kg / hr per tuyere, TiN powder, which blows at a rate of 410 kg / hr per tuyere Invention method-5, Method 6 according to the invention in which powder mixed at a weight ratio of TiN 0.97 to TiC1 is blown at a rate of 410 kg / hr per tuyere.
And Method 7 of the present invention in which metal Ti powder was blown at a rate of 480 kg / hr per tuyere. Table 2 shows the results of the experimental operation.

[0025]

[Table 2]

As is clear from Table 2, the number of days required for the hearth temperature to fall is reduced to less than half by using the method of the present invention, as compared with the conventional method of blowing titanium oxide alone. A quick action on the temperature rise of the section became possible. At the same time, as shown in Table 1, the Ti yield is dramatically improved as compared with the conventional titanium oxide injection alone, so the amount of titanium to be injected can be reduced, the trouble of tapping slag is reduced, and the cost of pig iron can be reduced. There was found.

[0027]

As described above, according to the present invention,
A titanium bear mainly composed of titanium carbide and / or titanium nitride for protecting a damaged portion of a hearth brick of a blast furnace,
It is formed quickly and stably at the damaged part of the hearth brick. As a result, a quick action can be taken against a rise in the temperature of the hearth caused by damage to the hearth brick. In addition, since the Ti yield is dramatically improved as compared with the conventional case where only titanium oxide is blown, the amount of titanium to be used can be reduced, and the hearth brick can be protected at a low cost at a low cost.
Life extension of the hearth brick and stable tapping slag are achieved.

Claims (3)

[Claims] 1. A method of blowing titanium carbide powder, titanium nitride powder or a mixture powder of titanium carbide and titanium nitride from one or a plurality of selected tuyeres provided in a blast furnace. Characteristic blast furnace operating method. 2. A method for operating a blast furnace, comprising blowing titanium metal powder from one or more selected tuyeres among the tuyeres arranged in the blast furnace. 3. A method for operating a blast furnace, comprising blowing a mixture powder containing titanium oxide and metallic aluminum from one or a plurality of selected tuyeres provided in the blast furnace.