JP2014224292A - Method for blowing dust coal from blast furnace tuyere - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more largely blow dust coal of low quality having a high SiOin Ash without increasing hot pig iron [Si] in a blast furnace operation in which dust coal is largely blown from a tuyere.SOLUTION: Provided is a method for blowing the fine coal of a plurality of coal kinds from the tuyere of a blast furnace using two fine coal lances, in which installing is performed in such a manner that the positions of the tips of the blow pipes of the two lances are shifted before and after, and the concentration of an SiOcomponent in the Ash of the fine coal blown from the lance on the side of a furnace wall is higher than the concentration of an SiOcomponent in the Ash of the fine coal blown from the lance on the inside of the furnace.

Description

  The present invention relates to a method for blowing pulverized coal from a blast furnace tuyere.

  In steelworks blast furnaces, coke is mainly used as fuel. In response to the depletion of coking coal, a raw material for coke, the amount of pulverized coal (hereinafter sometimes referred to as PC) has been increased. The method of blowing pulverized coal into the blast furnace is to insert a pulverized coal blowing pipe (hereinafter sometimes referred to as a lance) into the blow pipe that is a hot air blowing pipe into the blast furnace, and then blow it into the blast furnace tuyere. A method of burning pulverized coal in a way is common.

  There is a proposal of a blast furnace operating method in which a plurality of auxiliary fuel injection pipes are inserted into a blow pipe and a plurality of auxiliary fuels are injected when the auxiliary fuel is injected into the blast furnace (Patent Document 1). According to the proposal, heavy oil can be injected at the same time as pulverized coal, and various auxiliary fuel can be injected.

In recent years, there has been a demand for a technique for reducing the amount of coke used as an expensive high-coking coal as a raw material and blowing a large amount of inexpensive pulverized coal into a blast furnace.
There is a method of blowing a large amount of pulverized coal with a plurality of pulverized coal blowing pipes described in Patent Document 1 with respect to an increase in the amount of pulverized coal blowing (FIG. 1). According to this technology, the pulverized coal blowing load per one pulverized coal blowing pipe is reduced, which can contribute to an increase in the amount of pulverized coal blowing.
There is also a problem that the wear of tuyere increases in response to an increase in the amount of pulverized coal. For this, there is a proposal to define the tip position of the pulverized coal blowing nozzle so that the tip shape faces the tuyere side (Patent Document 2).
However, as the amount of pulverized coal injection increases, the combustion of the pulverized coal does not finish completely in the front tuyere, and the carbon in the pulverized coal remains in the blast furnace core as unburned char. is there.

JP-A-1992-202613 JP 2007-131873 A

When pulverized coal is blown from the blast furnace tuyere, if the pulverized coal ratio (PCR) increases, the pulverized coal does not completely burn in the raceway at the tuyere, and unburned char enters the furnace core (coke packed bed). . The carbon C in the unburned char that has entered the furnace core reacts with SiO ₂ in Ash to generate (SiO) gas. When the hot metal dropping in the furnace comes into contact with (SiO) gas, (SiO) is reduced and absorbed, and [Si] in the hot metal rises. In the hot metal, [Si] is oxidized in the steelmaking process to become steelmaking slag. Steelmaking slag contains unreacted CaO and FeO that has been reoxidized during blowing. Therefore, it is difficult to reuse steelmaking slag compared to blast furnace slag, and the increase in steelmaking slag leads to an increase in costs for ironmaking and steelmaking. . On the other hand, since pulverized coal has a lot of SiO _{2 in} Ash and lower grade is cheaper, the blast furnace can reduce the cost by using much pulverized coal with much SiO _{2 in} Ash. How in blowing pulverized coal from the blast furnace tuyeres [Si] does not increase in the molten iron be used many inexpensive pulverized coal in SiO ₂ are many low-grade Ash is desired.

An object of the present invention is to provide a pulverized coal injection process from a blast furnace tuyeres be used many inexpensive pulverized coal in many low-grade Ash in SiO ₂ in the molten iron [Si] does not increase.

The inventor blows pulverized coal having a high SiO ₂ component concentration in Ash from the pulverized coal blowing lance on the furnace wall side, and blows pulverized coal having a low SiO ₂ component concentration in the Ash from the pulverized coal blowing lance inside the furnace. Thus, it has been found that even if a large amount of inexpensive pulverized coal is blown, the rise of Si in the hot metal can be prevented.
The present invention has been made to solve the above-mentioned problems based on this finding, and the gist thereof is as follows.

(1) A method of blowing pulverized coal of a plurality of coal types from the blast furnace tuyeres using two pulverized coal lances. SiO ₂ component concentration in Ash pulverized coal blown from the wall lance, pulverized coal from a blast furnace tuyere being higher than SiO ₂ component concentration in Ash pulverized coal blown from the furnace inside of the lance Blowing method.
(2) The method of injecting pulverized coal from a blast furnace tuyere according to claim 1, wherein an interval between the position of the lance tip on the furnace wall side and the position of the lance tip on the furnace inner side is 50 mm to 150 mm. .

The present invention has thus Si in even hot metal by using a number of inexpensive pulverized coal is increased by SiO ₂ Many low-grade Ash, it can be blown pulverized coal from the blast furnace tuyeres.

The figure which shows the pulverized-coal blowing lance with the same front-end | tip position. The figure which shows the pulverized-coal blowing lance which shifted the front-end | tip position. The figure which shows the gas component and temperature in a raceway. The figure which shows a raceway simulation combustion experiment apparatus.

When pulverized coal is blown from the tuyere of the blast furnace, a pulverized coal lance is inserted into the blow pipe 1 so that the pulverized coal is blown out before the tip of the tuyere. If the amount of pulverized coal blown (PCR) is large, two lances can be installed and blown (Fig. 1. Double lance structure). in this case,
A blowing lance 2 having the same blowing position is used. In contrast, in the present invention, when blown using two pulverized coal injection lance multiple coal type of pulverized coal was placed staggered pulverized coal lance as in FIG. 2, Ash in the SiO ₂ component The operation is performed such that pulverized coal having a high concentration is blown from the lance 3 on the furnace wall side and pulverized coal having a low SiO ₂ component concentration in the Ash is blown from the lance 4 on the furnace inner side.

FIG. 3 shows an example of the gas components and the heat insulation temperature in the tuyere front raceway (FIGS. 5 and 34 of Japan Iron and Steel Institute 4.1 Edition 020105). The reaction of the front tuyere raceway is as shown in the following formulas (1) to (4). That is, the pulverized coal blown from the pulverized coal blowing lance is heated by hot air, and when it reaches a certain temperature or higher, first, volatile matter (which may be referred to as VM (CmHn)) is released (1). Volatile matter is burned by oxygen in the hot air to generate heat and become high-temperature combustion gas (2). This heat raises the temperature of the solid component in the pulverized coal and reacts with oxygen in the hot air (3). When oxygen is consumed, CO ₂ or H ₂ O of the combustion product gas and solid carbon react with each other to gasify and consume solid carbon (4). A part of these series of reactions proceeds in parallel.

PC (Temperature rise) → VM (CmHn) + C (1)
VM (CmHn) + O ₂ → CO ₂ + H ₂ O (2)
C + O ₂ → CO ₂ , C + (1/2) O ₂ 2 → CO (3)
C + CO ₂ → 2CO, C + H ₂ O → CO + H ₂ (4)

In FIG. 3, there is a CO ₂ component and temperature peak at a position about 1 m from the tip of the tuyere. When the amount of pulverized coal injection increases, the amount of volatile matter released by the above equation (1) increases, and the temperature peak moves to the furnace wall side due to combustion by the equation (2), and the heat load on the furnace wall side increases. There is. On the other hand, a countermeasure can be considered in which the tip position of the pulverized coal blowing lance is shifted to the inside of the furnace to suppress an increase in the heat load on the furnace wall side.

On the other hand, when the tip position of the pulverized coal blowing lance is shifted to the inside of the furnace, char that has not completely combusted in the raceway (hereinafter referred to as unburned char) enters the coke packed bed of the furnace core, There is a problem that the generation of (SiO) gas increases and the concentration of [Si] in the hot metal increases. That is, the unburnt char is mainly composed of solid carbon, but also includes an Ash component in pulverized coal. When unburned char heated to the high temperature on the raceway enters the furnace core having a low oxygen potential, carbon C in the unburned char and SiO _{2 in} Ash react to each other, and (SiO) Gas is generated.
When (SiO) gas comes into contact with the hot metal dropping in the furnace core, Si is absorbed by the hot metal according to the following formula (6), and the [Si] concentration in the hot metal is increased.

SiO ₂ + C → (SiO) + CO (5)
(SiO) + [C] → [Si] + CO (6)

The present inventor considered a policy of shifting the two lances and injecting pulverized coal as a method of solving the above conflicting problems.
Since the pulverized coal blown from the lance 3 on the furnace wall side undergoes the reactions (1) to (4) in advance, there is little generation of unburned char that cannot be burned on the raceway and enters the furnace core. Combustion is completed in the raceway and all solid carbon is gasified, and the ash that does not burn remains as a solid, but the oxygen partial pressure is high in the raceway, so there is no reduction of SiO ₂ and there is no C in the residual ash Therefore, generation of (SiO) gas does not occur.
On the other hand, the pulverized coal blown from the inside of the furnace cannot be burned in the raceway, and unburned char that enters the furnace core is generated, but if pulverized coal with little SiO ₂ is selectively blown, (SiO) gas The generation amount can be reduced, and an increase in the heat load on the furnace wall side can be suppressed.

Therefore, in the present invention, the pulverized coal having a high SiO ₂ in Ash is used to reduce the unburned char in the furnace core by shifting the tip position of the pulverized coal blowing lance toward the furnace wall, and the molten iron [Si] concentration is reduced. Prevent the rise. On the other hand, the pulverized coal with low SiO ₂ in the Ash is supposed to suppress an increase in the heat load on the furnace wall side by shifting the tip position of the pulverized coal blowing lance to the inside of the furnace.

  The tip position of the pulverized coal blowing lance should be adjusted in consideration of the volatile content of each pulverized coal, but it is preferable to shift the tip positions of the two lances within a range of about 50 to 300 mm. That is, when the length is 50 mm or less, the effect of shifting the two lances is hardly exhibited. If it is shifted by 300 mm or more, the combustion of the volatile matter of the pulverized coal from the lance on the furnace wall side starts in the blow pipe, which is not desirable because the temperature in the blow pipe and the furnace wall becomes high.

(Raceway furnace experiment)
Using a raceway simulation combustion furnace experimental apparatus as shown in FIG. 4, an experiment was conducted in which two types of pulverized coal (PC) were blown from different lances and burned under the experimental conditions shown in Table 1. Table 2 shows the compositions of the high SiO ₂ pulverized coal (a) and the high SiO ₂ pulverized coal (b) used. The raceway simulation combustion furnace test apparatus includes a lower furnace 5 and a central furnace 6, and the central furnace 6 can be removed for the convenience of sampling the furnace contents of the lower furnace 5 after the test. Coke is charged from the upper part of the central furnace 6. The coke and pulverized coal blown from the tuyeres 7 of the lower furnace are combusted in the tuyere front raceway 8. After the test, the raceway was dismantled to investigate unburned char of pulverized coal and accumulated dust. Dust was collected from a location located 300 mm above the center of the tuyere and 300 mm from the furnace wall, and component analysis of SiO ₂ and Al ₂ O ₃ was performed.

When the conventional lance arrangement (1), that is, when two lances are aligned at a position 50 mm from the tip of the tuyere and pulverized coal is ejected, the ratio of SiO ₂ / Al ₂ O _{3 in} the accumulated dust is 1.5. On the other hand, the lance arrangement (2) of the present invention system, that is, the pulverized coal ejection position from the two lances is shifted from the tip of the tuyere to the front and the tip of the tuyere, and the high SiO ₂ pulverized coal (a) is placed. When low SiO ₂ pulverized coal (b) was ejected from the lance at the tip of the tuyere from a lance 100 mm in front, the ratio of SiO ₂ / Al ₂ O _{3 in} the accumulated dust was 2.0. . In contrast, the average SiO ₂ / Al ₂ O ₃ ratio of the original pulverized coal is 2.3. Even if pulverized coal burns, Al ₂ O ₃ is considered to remain in the ash as it is, so the amount of SiO ₂ / Al ₂ O _{3 that} has been reduced is the amount of SiO ₂ volatilized and reduced as (SiO) gas. It is thought that. Therefore, it is considered that the amount of (SiO) gas generated can be reduced by the lance arrangement of the present invention system (2) compared with the lance arrangement of the conventional system (1), and the hot metal [Si] can be reduced in an actual furnace. Conceivable.

In blast furnace operation in which a large amount of pulverized coal is blown from the tuyere, it can be used to blow more low-quality pulverized coal having a high SiO ₂ component in Ash without increasing the amount of molten iron [Si].

  DESCRIPTION OF SYMBOLS 1 ... Blow pipe, 2 ... Blowing lance with the same blowing position, 3 ... Lance on the furnace wall side, 4 ... Lance inside a furnace, 5 ... Lower furnace, 6 ... Middle furnace, 7 ... Tuyere, 8 ... Raceway.

Claims (2)

A method in which pulverized coal of a plurality of coal types is blown using two pulverized coal lances from a tuyeres of a blast furnace,
The two lance blow pipe tip positions are shifted back and forth, and the SiO ₂ component concentration in the ash of the pulverized coal blown from the lance on the furnace wall side is in the ash of the pulverized coal blown from the lance inside the furnace. A method for injecting pulverized coal from a blast furnace tuyere characterized by being higher than the SiO ₂ component concentration.   The method for injecting pulverized coal from a blast furnace tuyere according to claim 1, wherein an interval between the position of the lance tip on the furnace wall side and the position of the lance tip on the inside of the furnace is 50 mm to 150 mm.

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