KR102026765B1 - Method of operating top and bottom blowing converter - Google Patents

Abstract

(Problem) In the decarburization refining process using a low-lowering converter, a method of operating a low-lowering converter capable of suppressing the vibration of the furnace body and the generation of dust and suppressing the wear of the furnace wall refractory material is proposed. .
(Solution means) The oxygen jet from the lance nozzle is sprayed at a nozzle inclination angle inclined with respect to the central axis of the above-mentioned uptake porous lance using a uptake porous lance having a plurality of oxygen gas injection lance nozzles. furnace bottom) is provided with n low odor vents, and in operation of the upper odor converter for blowing the gas for stirring from the low odor vents, a firing point formed by the impingement of oxygen jets injected from the blast porous lance collides with the molten iron bath surface. And a method of operating a low-lowering converter having an interference degree (IR) of 0.7 or less, which represents the degree of the relationship between the gas floating region for agitation which is blown into the molten iron from the low-intake vent and floats and is formed on the molten iron bath surface.

Description

Operation method of upper and lower odor converter {METHOD OF OPERATING TOP AND BOTTOM BLOWING CONVERTER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a top and bottom blowing converter effective in suppressing the generation of wear and dust of furnace wall refractory materials.

In the operation of the upper and lower scavenging converter, in particular, decarburization and refining, an operation in which the oxygen gas supply amount per unit time is increased in order to improve productivity. However, increasing the supply amount of oxygen gas means that iron is easily scattered as dust, and there is a phenomenon in which it adheres to surrounding equipment, furnace side walls, or furnace mouths. This dust is generated when bubbles generated in the furnace are separated from the molten iron bath with grained iron (so-called "bubble burst"), and are generated when iron atoms evaporate (so-called fume). It is known that the rate of occurrence changes as the decarburization and refining progress.

Further, in the decarburization and refining, the hot metal gradually decreases as carbon in the decarburization proceeds, so that finally, the molten steel becomes molten steel, but the molten steel and the molten steel can be clearly distinguished. In the following description, molten iron and molten steel are collectively referred to as "molten iron".

The scattered dust (iron powder) is recovered from whatever causes and is reused as an iron source. However, the recovery of iron from dust has a problem of increasing the work cost and causing a decrease in the operation rate of the low-lowering converter. Therefore, in the operation | work at the time of the decarburization refinement | purification of a top bottom smelting converter conventionally, suppressing generation | occurrence | production of dust is examined.

For example, Patent Literature 1 discloses a technique focusing on a high temperature reaction region (so-called "fire point") exceeding 2000 ° C. formed by the oxygen jet injected from each lance nozzle of the upper lance hitting the molten iron bath surface. . That is, the method which suppresses dust generation by defining the state in which neighboring fire points overlap each other by the index value called an overlap ratio, and adjusting the injection angle of the oxygen jet from a blowing lance so that the value will be 20% or less. to be.

In addition, Patent Literature 2 uses an indentation porous lance having seven holes including a center hole, and has an overlap ratio of 30% or less, and the amount of the fire point occupying the area surrounded by the outermost circumference of the fire store. The technique which suppresses dust by adjusting the injection angle of the oxygen jet from a top lance so that the ratio of a total area may be 75% or less is disclosed.

These techniques suppress the generation of dust due to bubble bursts by suppressing mutual interference of oxygen jets injected from the upper lance. However, it cannot be said that it is an effective technique for suppressing the dust due to fume.

On the other hand, in the decarburization refining, it is known that molten iron contained in the upper odor converter is oscillated by an oxygen jet injected from the upper lance or a stirring gas (for example, an inert gas, an oxidizing gas, etc.) supplied from the low odor blowing port. The fluctuation of the molten iron promotes the scattering of dust (particularly dust caused by bubble burst). Therefore, it can be said that suppressing fluctuation of molten iron and vibration of the furnace body is important for suppressing the generation of dust. In addition, suppression of the vibration of the furnace body also has the effect of preventing equipment failure.

Patent document 3 adjusts the injection angle of an oxygen jet to the range of 20-30 degrees so that the area | region which the flash point formed by the oxygen jet sprayed from an upper lance and the area | region which the gas for stirring supplied from the low odor blowing port floats may not overlap. The technique which suppresses the vibration of a furnace body is disclosed. However, when the injection angle of an oxygen jet is increased excessively, the refractory material of an upper bottom blowing converter will become easy to wear out.

In addition, scattering of molten iron and molten slag (so-called slopping) adheres to the furnace wall or the furnace duct in the same manner as dust caused by bubble burst or fume, and when it is deposited, it interferes with the operation of the low-lowering converter. It must be prevented because it causes.

Patent Literature 4 discloses a technique of suppressing spitting by arranging a low odor tuyeres inside a circle formed of a plurality of fire points. However, since the hot spots are arranged near the furnace wall, the furnace wall refractory material of the low bottom converter is easily damaged.

Japanese Laid-Open Patent Publication No. 60-165313 Japanese Laid-Open Patent Publication No. 2002-285224 Japanese Laid-Open Patent Publication No. 58-16013 Japanese Laid-open Patent Publication 2013-142189

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art, to suppress the vibration of the furnace body and the generation of dust in the operation of the decarburization refiner in the upper-lower converter, and to suppress the wear of the furnace wall refractory material. It is in suggesting the operation method of the low odor converter which can be done.

In order to further improve the technique disclosed in patent documents 1-4, the inventors carried out the oxygen jet from the upper lance (henceforth "the upper porous lance") which has a some lance nozzle (oxygen jet injection nozzle). Considering the mutual interference between each other, the flash point formed by the oxygen jet from a top blowing lance, and the mutual interference of the gas floating region for agitation supplied from the low blowing fan, it examined and repeated. As a result, to suppress the wear and tear of the furnace wall refractory material of the top bottom converter, and to suppress the generation of dust,

(a) Number of lance nozzles (e.g., Laval nozzles, straight nozzles, etc.) or injection angles that inject oxygen jets from the above-mentioned porous lances, in particular oxygen jets, to the molten iron surface accommodated in the upper bottom converter. To titrate and,

(b) arranging such that the flash point formed by the oxygen jet from the intake porous lance and the gas floating region for agitation supplied from the low intake tuyere do not interfere with each other, etc.

I found this to be valid.

That is, the present invention, using the uptake porous lance having a plurality of oxygen gas injection lance nozzle, the injection of the oxygen jet from the lance nozzle to the nozzle inclination angle θ (°) inclined with respect to the central axis of the uptake porous lance In addition, n lower odor vents are provided at the furnace bottom, and the upper oxygen blast furnace blown from the above-mentioned porous lance is supplied to the molten iron bath surface in the operation of the upper odor converter which blows the gas for stirring at the lower vent. In relation to the positional relationship between the flash point formed by colliding and the gas floating region for stirring that is formed in the molten iron bath surface by floating in the molten iron from the low blowing tuyeres, the central axis of the indentation porous lance in the molten iron bath surface in the low-lowering converter. In the plane perpendicular to the plane, the point where the center axis of the intake porous lance intersects the plane is the lance center point L _C , That the injection direction of the oxygen jet is injected from the lance nozzle intersecting the plane with the jet injection point (G _J), and then the center point is the center axis of that jeochwi tuyere outlet the point intersecting the plane (M _C ), The interference degree IR represented by the following formula (1) is 0.7 or less.

IR = ∑ [(r _t / r _bi ) × (90-φ _i ) / 90] / n... (One)

only,

IR: interference,

n is an integer of 2 or more,

φ: an angle (°) formed by a line connecting the lance center point (L _C ) and the jet injection point (G _J ), and a line connecting the lance center point (L _C ) and the tuyere center point (M _C ),

r _t : distance (m) between the lance center point (L _C ) and the jet injection point (G _J ),

r _b : distance (m) between each of the blowhole center points (M _C ) and the lance center point (L _C ) of the low odor blowhole;

Further, φ _i and r _bi are angles (°) and distances (m) required when the low-intake vents of the i-th (i: 1 to n) are respectively.

Moreover, in the said operation method of this invention,

(1) The interference degree IR satisfies (IR) ≤ 0.70 when the angle φ representing the positional relationship between the lance nozzle and the low blowing vent is minimum.

(2) the interference degree (IR) is 0.46 or less,

(3) The lance nozzle should be a Laval nozzle or a straight nozzle,

(4) The above-mentioned upsetting porous lance should have 2 to 5 lance nozzles,

(5) The combination of the upper lance and the lower blast tuyere shall be operated so as to satisfy the interference degree IR.

This is a more preferred embodiment.

According to the present invention, in performing decarburization and refining using the low bottom converter, it is possible to suppress the generation of dust and improve the iron yield, and to suppress the vibration of the furnace body to effectively prevent wear of the furnace wall refractory material. can do.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view schematically showing a relationship between a top odor porous lance and a top bottom converter applied to the present invention.
2 is a graph showing the relationship between the interference and the average dust generation rate.
3 is a graph showing the relationship between the interference and the refractory wear index.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows roughly the relationship of the upsetting porous lance and the low blowing tuyere which apply this invention. The upstream porous lance 1 has a plurality of oxygen gas injection lance nozzles 2, and the oxygen jet 3 can be injected from the respective lance nozzles 2. The z axis in FIG. 1 is the central axis of the uptake porous lance 1, and the molten iron bath surface is orthogonal to this axis (z = 0). Therefore, the distance h between the lower end of the uptake porous lance 1 and the molten iron bath surface becomes the lance height. And the plane perpendicular | vertical with respect to the central axis of the uptake porous lance 1 (henceforth "xy plane") is a molten iron bath surface prescribed by the x-axis and the y-axis. The point where the central axis of the uptake porous lance 1 intersects with the xy plane corresponds to the origin of the coordinate axis, hereinafter referred to as the lance center point L _C.

In addition, although the example in which two lance nozzles 2 were formed is shown in FIG. 1, about the number of these lance nozzles 2, it is not limited, It is preferable to set it as about 2-5 pieces.

The oxygen jet 3 injected from the uptake porous lance 1 is injected in the direction of an angle inclined with respect to the central axis of the uptake porous lance 1 (hereinafter referred to as "nozzle inclination angle θ (°)"). The point where the oxygen jet 3 intersects the xy plane corresponds to the center point of the firing point (ie, a high temperature reaction region exceeding 2000 ° C. formed by the oxygen jet impinging on the molten iron bath surface) 4. Hereinafter, this point is referred to as jet injection point (G _J). Any of the plurality of lance nozzles 2 formed on the uptake porous lance 1 all have the same direction nozzle inclination angle θ. Thus, the injecting oxygen jet 3 is also injected at the same angle.

On the other hand, a plurality of low odor blowers 5 (that is, i = 1 to n) are provided in the upper low odor converter (not shown). However, FIG. 1 exemplifies only one and hereinafter, this will be described as the i-th low odor blower 5. In addition, the gas for stirring supplied from the low odor blower 5 becomes a bubble, it floats in molten iron, and the area | region 6 (it is called "a stir gas floating area" for stirring) appears in this bubble.

For example, when letting the center axis | shaft of the low blowing vent 5 cross | intersect an xy plane as the blower center point M _C , in FIG. 1, the i-th blower center point M _C is shown like M _Ci .

When the angle φ (°) formed by the line connecting the lance center point L _C and the jet injection point G _J , and the line connecting the lance center point L _C and the tuyere center point M _C , is shown in FIG. In 1, the angle with the i-th low odor blower 5 is (phi) (( _i )).

In addition, the distance m between the lance center point L _C and the jet injection point G _J is set to r _t . In addition, since this distance r _t is the same in all the nozzle inclination angles (theta) of the some lance nozzle 2, the distance r _t prescribed | regulated for each lance nozzle 2 is also the same.

In addition, the distance m between the lance center point L _C and the tuyere center point M _C is set to r _b . However, in FIG. 1 are referred to as, _bi r to indicate that the distance r _b on jeochwi tuyeres 5 of the i-th.

Hereinafter, with reference to FIG. 1, an example of the operation method of an upper bottom blow converter according to this invention is demonstrated.

The inventors of the molten iron use an experimental low-lowering converter (capacity: 5 ton) capable of injecting an oxygen jet 3 from the air freshener lance 1 and supplying a gas for stirring from the low air blower 5. The decarburization and refining experiments were carried out to examine the effect of the arrangement of the top porous lance 1 and the low blowing tuyeres 5, in particular, on the amount of dust generation and the amount of wear of the refractory.

The upstream porous lance 1 uses a three-tube water-cooled system, and the tip thereof injects the oxygen jet 3 in a direction inclined at a nozzle inclination angle θ with respect to the central axis of the upstream porous lance 1. A plurality of lance nozzles 2 which can be provided were installed on the same circumference at equal intervals. In addition, the shape and dimension of the lance nozzle 2 are as showing in Table 1. In this experiment, oxygen gas (flow rate: m ³ / min (Normal)) was used as the oxygen jet 3, and argon gas was used as the gas for stirring. The lance height h was 400 mm. Injection of the oxygen jet 3 started when the carbon concentration in molten iron was 4.0 mass%, and stopped when it decreased to 0.05 mass%.

The combination which shows the relationship of the upsetting porous lance 1 and the low blowing fan 5 in this experiment is as showing in Table 2, Table 3, Table 4, Table 5. As shown in FIG. The interference degree IR shown in Table 2 and Table 3 is the molten iron from the flash point 4 formed by the upper oxygen jet 3 injected from the upper porous lance 1 colliding with the molten iron bath surface, and the low odor vent 5. It is the value computed by following formula (1) which shows the positional relationship of the gas floating area | region 6 for agitation blown in and floated and formed in the molten iron bath surface.

IR = ∑ [(r _t / r _bi ) × (90-φ _i ) / 90] / n... (One)

only,

IR: interference,

n is an integer of 2 or more,

φ: an angle (°) formed by a line connecting the lance center point (L _C ) and the jet injection point (G _J ), and a line connecting the lance center point (L _C ) and the tuyere center point (M _C ),

r _t : distance (m) between the lance center point (L _C ) and the jet injection point (G _J ),

r _b : distance (m) between each of the blowhole center points (M _C ) and the lance center point (L _C ) of the low odor blowhole;

Further, φ _i and r _bi are angles (°) and distances (m) required when the low-intake vents of the i-th (i: 1 to n) are respectively.

In this way, while performing the decarburization refining experiment, the dust concentration in the exhaust gas was measured, and the dust generation rate (kg / [minute / ton]) was calculated using the following Equation (2). In addition, the dust generation speed in Formula (2), the dust concentration in waste gas, and the waste-gas flow volume used the average value for each level of experiment. The relationship between the average dust generation speed and the said interference degree IR is shown in FIG.

Average dust generation rate (kg / [min, molton]) =

[Dust concentration (kg / m ³ (Normal)) × [Exhaust gas flow rate (m ³ (Normal) / [min, molten iron])] in the exhaust gas]

          … (2)

As is apparent from FIG. 2, as the interference degree IR decreases, that is, the interference (degree of relation) between the flash point 4 and the stirring gas floating region 6 decreases, the generation speed of dust decreases, When the interference degree IR was less than 0.70, it was less than the average dust generation rate in the maximum value 0.95 of the said interference degree IR in this experiment. Moreover, in the area | region whose interference degree IR is 0.46 or less, the average dust generation speed is drastically reduced to 1/2 or less of the maximum value of the average dust generation speed in the interference range of experiment.

In addition, when the said interference degree IR is 1.0, it means that the flash point 4 and the stirring gas floating region 6 overlapped completely.

After the experiment was completed, the MgO concentration (mass%) in the slag was measured at each level of the experiment, and the refractory wear index was calculated using the following Equation (3). In addition, as is apparent from Eq. (3), the refractory loss index of level 18 is 1.0. The relationship between the refractory wear loss index and the interference degree IR is shown in FIG.

Refractory wear index = MgO concentration (mass%) / in slag after the end of the experiment

            MgO concentration (mass%) in slag after level 18 experiment termination

   … (3)

As is apparent from FIG. 3, the influence of the interference degree IR on the refractory wear index is small, but the influence of the nozzle inclination angle θ is greater. That is, in the decarburization refining using the uptake porous lance 1 with the nozzle inclination angle θ of 23 °, the refractory wear index increases more than the decarburization refining using the uptake porous lance 1 with the nozzle inclination angle θ of 14 °, that is, the hand of the refractory It can be seen that the hair is easy to proceed.

From these experimental results, in the present invention, the interference degree IR is limited to 0.70 or less, preferably 0.46 or less.

That is, in order to make the interference degree IR computed by the above formula (1) into a small value, the low blowing vent 5 is arrange | positioned in the position far from the upper piercing lance 1, ie, the distance r _bi , respectively. It can also be seen that it is effective to arrange the firing point 4 and the gas floating region 6 for stirring in a distant position (that is, increase the angle φ _i respectively).

In addition, when the said nozzle inclination-angle (theta) is too big | large, since the area | region of the flash point 4 becomes close to the inner wall of an upper bottom draw path, and the problem which raises the wear of refractory arises, it is preferable to make nozzle inclination-angle (theta) less than 23 degrees.

As for the number of the lance nozzles 2 formed in the upsetting porous lance 1, five or less (so-called five holes) are preferable. The reason for this is that the size of the flash point 4 can be reduced by reducing the number of lance nozzles 2. As a result, the arrangement of the low odor vent 5 can increase the degree of freedom, and furthermore, the angle? Can be easily enlarged. In the combination of the upsetting porous lance 1 and the low blowing tuyere arrangement used in the experiment, the upsetting porous lance 1 capable of minimizing the interference IR has only the number of nozzles: 4 and 5 (Tables 2, 3, No. 4 and 5), and the number of nozzles: No. 6 or less No. 5 or less no. Of the novice porous lances 1 is not obtained in the arrangement satisfies the interference (IR) ≤ 0.46. It can be seen that it is preferable to use.

Example

The actual experiment of the upper blast furnace which decarburizes molten iron was performed using the actual upper blast converter (capacity 350 tons). Arrangement of the lance nozzle of the used uptake porous nozzle, and arrangement | positioning of the low odor tuyeres of a top bottom blow converter are as showing in Table 6. The lance nozzles use a Laval nozzle, and the throat diameter of the lance nozzles used by level A, B is 82.8 mm, and the exit diameter is 87.1 mm. The throat diameter of the lance nozzle used at the levels C and D is 74.0 mm, and the outlet diameter is 77.8 mm. The throat diameter of the lance nozzle used at level E, F is 67.6 mm, and the exit diameter is 71.1 mm. All of these lance nozzles are designed with an appropriate expansion pressure of 0.33 MPa.

In this operation experiment, firstly, iron scrap is charged into a top bottom converter, and then molten iron (temperature 1260 to 1280 ° C) subjected to dephosphorization in advance is charged to a top bottom converter, and then oxygen jets are carried out from the top porous lance. While spraying the molten iron bath surface, the gas for stirring is supplied from the low odor tuyeres, and as a manufacturing waste material, the quicklime of the amount which the basicity of the slag in the furnace is 2.5 is added, and the carbon concentration in the molten iron is reduced to 0.05 mass%. Decarburization was carried out until The components of molten iron are as shown in Table 7. In addition, basicity is the value computed by following formula (4).

Basicity = [mass% CaO] / [mass% SiO ₂ ]... (4)

[mass% CaO]: CaO concentration in slag in the furnace

[mass% SiO ₂ ]: SiO ₂ concentration in slag in the furnace

The oxygen jet used oxygen gas, and the stirring gas used argon gas. The flow rates of the oxygen jet and the gas for stirring and the lance height are as shown in Table 8.

In this way, decarburization and refining were carried out, and the time (minutes) required for refining, T.Fe (mass%) in slag at the time of blowing stop, dust generation rate, and refractory wear index were examined. The results are shown in Table 9. The interference degree IR computed from the arrangement of the used uptake porous lance and the low blowing tuyeres is as shown in Table 9. These values are the average values of decarburization and refining for each level. In addition, the dust generation speed | rate is shown as the relative value which makes the dust generation | occurrence | production rate of level F to 1, and the refractory wear loss index is shown as the relative value which makes the refractory head wear index of level F to 1.

As is clear from the results shown in Table 9, the invention examples (levels A and B) have the same T.Fe in the slag at the time of refining time and blowing stop compared to the comparative examples (levels C, D, E, and F). The dust generation rate can be greatly reduced. In particular, the level A was able to suppress the loss of the refractory.

1: deodorant perforated lance
2: lance nozzle
3: oxygen jet
4: fire store
5: low blower
6: gas floating zone for stirring

Claims (7)

Using an upstream porous lance having a plurality of oxygen gas injection lance nozzles, the oxygen jet from the lance nozzle is injected at a nozzle inclination angle θ (°) inclined with respect to the central axis of the upstream porous lance, furnace bottom) is provided with n low odor vents, and in the operation of the upper odor converter for blowing the gas for stirring from the low odor vents,
With respect to the positional relationship between the firing point formed by impingement of the upstream oxygen jet injected from the above upstream porous lance, and the floating gas floating region formed in the molten iron bath surface by floating in the molten iron from the low intake vent,
In the plane perpendicular | vertical with respect to the central axis of the above-mentioned uptake porous lance in the molten iron bath surface in the said bottom-lowering converter, the point where the center axis of the above-mentioned uptake porous lance intersects the plane is made into the lance center point L _C , and The point where the injection direction of the oxygen jet injected from the lance nozzle intersects the plane is the jet injection point G _J , and the point at which the central axis of the low blowing vent intersects the plane is the center of the blower outlet M _C. When you do,
The interference degree IR represented by following formula (1) is 0.7 or less, The operation method of an upper bleeding converter characterized by the above-mentioned.
IR = ∑ [(r _t / r _bi ) × (90-φ _i ) / 90] / n... (One)
only,
IR: interference,
n is an integer of 2 or more,
φ: an angle (°) formed by a line connecting the lance center point (L _C ) and the jet injection point (G _J ), and a line connecting the lance center point (L _C ) and the tuyere center point (M _C ),
r _t : distance (m) between the lance center point (L _C ) and the jet injection point (G _J ),
r _b : distance (m) between each of the blowhole center points (M _C ) and the lance center point (L _C ) of the low odor blowhole;
Further, φ _i and r _bi are angles (°) and distances (m) required when the low-intake vents of the i-th (i: 1 to n) are respectively. The method of claim 1,
And said interference degree (IR) is 0.46 or less. The method of claim 1,
And said lance nozzle is a Laval nozzle or a straight nozzle. The method of claim 2,
The said lance nozzle is a laval nozzle or a straight nozzle, The operation method of the upper bottom blow converter characterized by the above-mentioned. The method according to any one of claims 1 to 4,
The above-mentioned upsetting porous lance has a 2-5 lance nozzle, The operation method of an up-down blast converter characterized by the above-mentioned. The method according to any one of claims 1 to 4,
The operation of the upper dent converter is arranged by operating the combination of the upper lance and the lower blast tuyer to satisfy the interference degree IR. The method of claim 5,
The operation of the upper dent converter is arranged by operating the combination of the upper lance and the lower blast tuyer to satisfy the interference degree IR.

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