JP2007077492A - Blowing method for converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it difficult for the spitting granular irons as the stuck metal to stick to a furnace opening hole part. <P>SOLUTION: In a blowing method into a converter by performing oxygen-blowing from a top-blown lance 7 into the top-bottom blown converter, the oxygen-feeding velocity for blowing the oxygen from the top-blown lance 7 is adjusted based on superficial velocity of the waste gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a blowing method for a converter in which oxygen is blown into a converter from an upper blowing lance, for example.

Conventionally, as shown in Patent Document 1, in the operation of a converter, hot metal is charged into the converter (furnace body), and an upper blowing lance is inserted into the furnace port of the converter, and then from this upper blowing lance. Blowing is performed by blowing oxygen gas toward the hot metal. At this time, the hot metal is stirred by blowing gas from the bottom of the converter.
When oxygen gas is blown from the top blowing lance, the oxygen gas collides with the surface of the hot metal, so part of the hot metal flies to the furnace port as spitting particle iron, and this spitting particle iron enters the furnace port. Adhering to the bullion (hereinafter, the bullion adhering to the furnace port is called the adhering bullion).

For example, when charging scrap into the converter, the scrap chute that puts the scrap into the converter is clogged in the furnace mouth, because the adhering metal is deposited and deposited around the furnace opening. This causes a problem that scrap cannot be put into the converter.
Further, when a sub lance for measuring the temperature [° C.] of hot metal (molten steel) is inserted into the furnace body, there is a risk that the sub lance will collide with the adhered metal. Also, as the number of charges increases, the refractory at the bottom of the furnace body (furnace bottom) melts and decreases, and as a result, the vicinity of the furnace port gradually becomes heavier, and a tilting trip that makes it difficult for the converter to start up may occur. There is.

In this way, depositing adhering metal around the furnace port causes various problems, so if the adhering metal deposits more than a predetermined amount in the operation of the converter, for example, the adhering metal adhering to the furnace port using an oxygen pipe is used. After the gold is melted, the ingot is removed using a scrap chute or melted using a dedicated metal melting lance.
JP 2005-89839 A

However, the operation of the converter must be stopped during the removal work of the adhering metal, and there is a problem that productivity is lowered. In addition, there is a problem in that the refractory at the throttle portion of the furnace port may fall off together with the metal during the removal work of the attached metal, which shortens the converter life.
In order to solve such a problem, in the operation of the converter, the deposition rate of the adhering metal around the furnace port is decreased, that is, the spitting granular iron that becomes the adhering metal hardly adheres to the furnace port. Therefore, it is desired to reduce the removal work as much as possible. Therefore, a technique for preventing spitting granular iron from adhering to the furnace port by improving the lance tip has been considered, but the actual situation is that a sufficient effect has not been obtained.

  Therefore, in view of the above problems, an object of the present invention is to provide a method for blowing a converter in which spitting granulated iron that becomes an adhering metal hardly adheres to a furnace port.

  In order to achieve the above object, the present invention has taken the following measures. That is, the technical means for solving the problems in the present invention is a method of blowing a converter in which oxygen is blown from the top blowing lance to the molten iron in a top bottom blowing converter, It exists in the point which adjusts an acid delivery speed | rate so that Formula (1) may be satisfy | filled.

The inventor has found the superficial velocity at which no metal is attached to the furnace port when oxygen is blown, that is, the acid feeding rate, through various experiments.
That is, by adjusting the acid feed rate so as to satisfy the formula (1) at the time of blowing, it is possible to make it difficult for spitting granulated iron to be attached to the furnace mouth and to produce in the converter. It was found that the property can be improved.
Immediately after the start of blowing, there is not much slag (cover slag) covering the hot metal surface, and if this cover slag is low and the acid feed rate is increased, oxygen directly hits the hot water surface. Since spitting grain iron easily jumps up, it is preferable to reduce the acid feed rate when the cover slag is low and to increase the acid feed rate and shorten the blowing time when the cover slag is large. That is, it is preferable to determine the acid feed rate according to the degree of cover slag formation.

  Therefore, as a result of various experiments, the inventor satisfies the formula (2) when the integrated amount from the start of oxygen blowing from the top blowing lance exceeds 40% of the total oxygen amount. It was found that the acid feed rate was adjusted.

According to this, when the total amount of oxygen blown to the hot metal exceeds 40% of the total amount of oxygen blown (total oxygen amount), the lower limit value of the acid feed rate is reached. Blowing time can be shortened by raising.
In addition, it is preferable to adjust the acid feed rate so as to satisfy the formula (3) until the integrated amount from the start of the blowing of oxygen blown from the top blowing lance reaches 40% of the total oxygen amount.

  According to this, for the time until the integrated amount reaches 40% of the total oxygen amount, by lowering the lower limit value of the acid feed rate, it becomes difficult for the spitting grain iron to jump up, and the spitting grain It is possible to prevent iron from attaching to the furnace opening as much as possible.

  According to this invention, it becomes difficult for spitting granular iron used as adhesion metal to adhere to a furnace mouth.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall side view of a converter for performing the blowing method for a converter according to the present invention. The converter is not limited to this embodiment. The converter is an upper-bottom blowing converter capable of blowing oxygen from the upper side of the furnace body and blowing gas from the bottom of the furnace body, and can accommodate hot metal (molten steel), scrap, etc. in the furnace body 1 It has become.
The furnace body 1 is composed of a bottomed and cylindrically formed iron shell 2 and a plurality of refractories 3 (refractory bricks) provided inside the iron shell 2. A gas blowing portion 5 for blowing gas is provided at the bottom portion 4 of the furnace body 1, and a furnace port 6 is formed on the side facing the gas blowing portion 5, that is, in the upper portion of the furnace body 1 in FIG. 1. . An upper blowing lance 7 for blowing oxygen or the like into the furnace port 6 can be inserted.

The iron skin 2 has a bottom portion 10, an enlarged portion 11 whose inner diameter and outer diameter gradually increase from the bottom portion 10 toward the furnace port 6, and a continuous inner diameter and outer diameter from the enlarged portion 11. It has a constant straight body 12 and a throttle part 13 whose inner and outer diameters gradually decrease from the straight body 12 toward the furnace port 6 side.
The refractory 3 is affixed in order in the iron shell 2 along the bottom part 10, the enlarged part 11, the straight body part 12, and the throttle part 13 of the iron skin 2, and the inner surface of the affixed refractory 3 is It is substantially along the inner surface of the iron skin 2. A hot water outlet 9 (outgoing steel outlet) is formed in the straight body portion 12 of the iron skin 2 for hot metal 8 (molten steel).

In the furnace body 1, a furnace expansion portion 15 whose outer diameter or inner diameter gradually increases is formed by the iron shell 2 and the refractory 3, and is continuously formed in the furnace expansion portion 15, and the outer diameter or inner diameter is substantially constant. A furnace straight body portion 16 and a furnace throttle portion 17 whose outer diameter or inner diameter decreases as going from the furnace straight body portion 16 to the furnace port 6 are formed.
According to the above converter, after the hot metal is charged into the furnace body 1 and the upper blowing lance 7 is inserted into the furnace port 6 of the furnace body 1 (converter), the upper blowing lance 7 is directed toward the hot metal. Blowing can be performed by blowing oxygen gas. When blowing, gas is blown from the bottom of the furnace body 1 to stir the hot metal.

In the blowing method of the present invention, the acid feed rate Fo ₂ when oxygen is blown from the top blowing lance 7 is adjusted so as to satisfy the formula (1). That is, in blowing in the dephosphorization process or the decarburization process, oxygen is blown with the upper blowing lance 7 so as to satisfy the formula (1).

In the formula (1), the furnace port inner diameter R is the inner diameter of the refractory 3 provided at the outermost end of the furnace restrictor 17 (the restrictor 13 of the iron shell 2), more specifically, the inner surface of the leftmost end refractory 3a. To the inner surface of the rightmost end refractory 3b.
Equation (1) is derived from various experiments.
Hereinafter, the derivation process of the equation will be described.
The inventor investigated what kind of spitting granular iron adhered to the furnace port 6 by past operations and experiments. After the operation is completed, the adhering metal attached to the furnace port 6 is collected, and the cross-sectional area and composition analysis are performed. I understood.

Accordingly, the inventors superficial velocity V, i.e., by changing the oxygen-flow-rate Fo _2, was examined by the blowing state (operating state) of each oxygen-flow-rate Fo ₂ simulations and experiments operations.
2 and 3 show the results. 2 and 3, the total amount of oxygen blown per charge is set to 100%, and the period until the cumulative amount of oxygen blown up to 40% of the total oxygen amount is initial, and the cumulative amount is equal to the total oxygen amount. The results are summarized with the period exceeding 40% as the middle term and beyond.
As shown in FIGS. 2 and 3, the total amount of main raw materials (for example, hot metal, waste metal, and cold iron) to be put into the furnace height (H) and the furnace body (converter) is constant. In the experiment, the blowing conditions were set as shown in Table 1.

  In addition, the converter charging molten iron component, the molten steel component at the time of blowing the converter, and the auxiliary raw material charged into the molten iron were set within the ranges shown in Tables 2 and 3.

The operation status includes the blowing time (min / ch) in each operation, the amount of dust generated per ton of molten steel (kg / t), the interval of collecting metal (ch / time), that is, removal of adhered metal The total number of charges that can be operated before the removal work is started again, heat dissipation loss (Mcal / t), iron ore input (kg / t),
The steel yield and the steel output (t / ch) were examined.
Based on each of the above operating conditions, steel yield, steel output (t / ch), steelmaking time (min / ch), metal removal time (min / ch), production pitch (ch / day), production The ability (kt / day) was determined.

The steelmaking time is the sum of 15 minutes as the time required for main raw material charging, refining, steel extraction, and waste removal to the blowing time. The bullion collecting time is set to 30 minutes for one bullion collecting time, and this time is divided by the bullion collecting interval to obtain the bullion collecting work time per charge. The production pitch is the total number of charges that can be made per day, that is, the operation time / the time required for one charge.
The time required for one charge is the sum of the steel making time and the metal collecting time. The production capacity (kt / day) was calculated by the product of the production pitch and the amount of steel output.

FIG. 4 is a graph in which the horizontal axis represents the superficial velocity V in the simulation and the experimental operation described above, and the production capacity represents the vertical axis. As can be seen from FIG. 4, as the value of the superficial velocity V increases from 13.5 m / sec as a boundary, the production capacity decreases in both the initial stage and the middle stage.
When the superficial velocity V increases, spitting granular iron easily adheres to the furnace port 6 even at the same acid feed rate Fo ₂ . That is, when the superficial velocity V is high, frequent bullion removal work must be performed about once every several charges, and the production pitch decreases due to the influence, and the production capacity decreases.

Conversely, as the superficial velocity V becomes smaller at 13.5 m / sec, the production capacity decreases in both the initial and middle periods. Under the condition that the superficial velocity V becomes small, that is, as is apparent from the equation (1A), the acid feed rate Fo ₂ decreases. When the acid feed rate Fo ₂ is decreased or the furnace port inner diameter R is increased, for example, it takes time for the decarburization process or the heat radiation loss is large, and the blowing time becomes longer due to this influence.
As described above, according to the simulation and the experimental operation, the superficial velocity V when oxygen is blown has a good range of 13.5 m / sec or more and 17.5 m / sec or less. It became so.

Therefore, by controlling the superficial velocity V, that is, the acid feed rate Fo ₂ so as to satisfy the expression (1), it becomes difficult to attach the metal to the furnace port 6 and the productivity can be improved.
When the amount of oxygen blown from the top blowing lance 7 and the amount of exhaust gas discharged from the furnace port 6 are considered to be equal, the relational expression between the superficial velocity V of exhaust gas and the acid feed rate Fo ₂ is expressed by the equation (1A). )It can be expressed as. In deriving the formula (1A), the exhaust gas was CO gas generated by reacting all of the oxygen blown by the top blowing lance 7 with the carbon C in the hot metal. The temperature of the exhaust gas was set to 1573K, the temperature of the oxygen blown was set to 298K, and thermal expansion was taken into consideration.

Now, in blowing, it is preferable to blow oxygen with the top blowing lance 7 so as to satisfy the formula (1), but the cover slag S is not formed so much on the hot metal surface immediately after the blowing. Without increasing the cover slag S, if the superficial velocity V is increased, that is, the acid feed rate Fo ₂ is increased, the spitting granular iron tends to jump up and the spitting granular iron easily adheres to the furnace port 6. Become. Therefore, in the period spitting grain iron have reduced the oxygen-flow-rate Fo ₂ in timing cover slag S is less in order not to adhere to the furnace opening 6, the cover slag S could sufficiently be, oxygen-flow-rate Fo ₂ It is better to shorten the blowing time by increasing.

Therefore, the inventor conducted various experiments, and as shown in FIG. 4, when the cumulative amount of oxygen blown in the top blowing lance 7 exceeded 40% with respect to the total oxygen amount, in other words, In the middle of blowing, the lower limit of the superficial velocity V is increased. That is, it is preferable to raise the lower limit of the acid feed rate Fo ₂ .
Therefore, when the integrated amount exceeds 40% of the total oxygen amount, the acid feed rate Fo ₂ is set so as to satisfy the formula (2) in which the lower limit value of the superficial velocity V is 14.5 m / s. It is good to adjust. At this time, when viewed from the carbon content (%), it is preferable to adjust the acid feed rate Fo ₂ so as to satisfy the formula (2) until the carbon content [C] becomes 0.2% or less.

That is, the acid feed rate Fo ₂ is adjusted so as to satisfy the formula (2) until the integrated amount exceeds 40% of the total oxygen amount and the carbon amount [C] decreases to 0.2% or less. It is preferable to do this.

Further, at the initial stage of blowing until the integrated amount reaches 40% with respect to the total oxygen amount, the cover slag S is not formed so much, so it is preferable to reduce the acid feed rate Fo ₂ . As shown in FIG. 4, the upper limit value of the superficial velocity V is decreased until the integrated amount reaches 40% with respect to the total oxygen amount. That is, it is preferable to lower the upper limit value of the acid feed rate Fo ₂ .
Therefore, until the integrated amount reaches 40% of the total oxygen amount, the acid feed rate Fo ₂ is set so as to satisfy the equation (3) in which the upper limit value of the superficial velocity V is reduced to 16.5 m / s. It is good to adjust.

5 and 6 show the operation of the converter (decarburization with dephosphorization) by changing the acid feed rate Fo ₂ . 5 and 6, the total amount of oxygen per charge by blowing is 100%, and the total amount of oxygen blown is less than 40% of the total oxygen amount, the initial stage of blowing is the initial amount. When the total amount of oxygen is 40% or more and less than 90%, the middle stage of blowing is used, and when the cumulative amount of oxygen blown reaches 90% or more of the total amount of oxygen, the final stage of blowing is performed. ₂ was changed. In the operation of this converter, the blowing conditions are set as shown in Table 1, and the molten steel component at the time of converter charging, the molten steel component at the time of blowing the converter, and the auxiliary materials to be charged into the molten iron are in the ranges shown in Tables 2 and 3. Set in.

As can be seen from FIG. 5, it is possible to secure a production capacity of 10 (kt / day) or more by adjusting the acid feed rate Fo ₂ so as to satisfy the formula (1) or the formula (2) at least in the middle of blowing. In addition, it was possible to secure a bullion collection interval of 9 (ch / time) or more (removing bullion at a rate of once per 9 charges).
In addition, by adjusting the acid feed rate Fo ₂ so as to satisfy the formula (3) at least in the initial stage of blowing, the average bullion collecting interval could be increased as compared with those not satisfying the above formula. .

As shown in FIG. 6, the production capacity is less than 10 (kt / day) in Comparative Examples 1 to 3 that do not satisfy any of Formulas (1) to (3) compared to Examples 1 to 6 of the present invention. (Especially around 9.0), which is inferior to the embodiment of the present invention. In addition, the bullion removal interval is 5.0 (ch / time) or less except for Comparative Example 1, and the bullion removal work must be performed at least once every 5 charges. It is inferior to the embodiment of the present invention because it needs to be frequent.
The blowing method of the present invention is applicable to both dephosphorization treatment and decarburization treatment as long as oxygen is blown from the top blowing lance 7 in an upper bottom blowing converter. It is possible.

  In the above embodiment, the initial stage of blowing is when the integrated amount of oxygen is up to 40% of the total oxygen amount, but the time when the integrated amount becomes 30 to 50% of the total oxygen amount is blown. It may be initial. In this case, corresponding to the initial stage of blowing, the middle stage of blowing is the period when the integrated amount is 30 to 50% or more with respect to the total oxygen amount.

It is the whole converter side view. It is the result of the operation and productivity simulation which were carried out by changing the conditions of the furnace port inner diameter and the acid feed rate in the early stage of blowing. It is the result of the operation and productivity simulation which were carried out by changing the conditions of the inner diameter of the furnace port and the acid feed rate from the middle to the final stage of blowing. It is a relationship figure of the superficial velocity of exhaust gas, and production capacity. The Example which implemented the blowing method of this invention is put together. The comparative examples are summarized.

Explanation of symbols

1 Furnace 2 Iron skin 3 Refractory (Refractory brick)
6 Furnace

Claims (3)

In the blowing method of the converter in which oxygen is blown from the top blowing lance to the hot metal in the top bottom blowing converter,
A method for blowing a converter, wherein an acid feed rate of the upper blowing lance is adjusted so as to satisfy Formula (1).

When the integrated amount from the start of the blowing of oxygen blown from the upper blowing lance exceeds 40% of the total oxygen amount, the acid feed rate is adjusted so as to satisfy the formula (2). The method for blowing a converter according to claim 1.

The oxygen delivery rate is adjusted so as to satisfy the formula (3) until the integrated amount from the start of the blowing of oxygen blown from the upper blowing lance reaches 40% of the total oxygen amount. Item 3. A converter blowing method according to Item 1 or 2.

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