JP3509128B2 - Operating method of converter type smelting reduction furnace and oxygen blowing lance - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operating method for smelting and reducing a chromium-containing or iron-containing raw material such as chromium ore or iron ore in a converter-type smelting reduction furnace (abbreviated as converter hereinafter) having a top-bottom blowing function. It concerns the improvement of the top blowing lance.

[0002]

2. Description of the Related Art In a process of adding an ore raw material such as chromium ore or iron ore and a carbonaceous material such as coke into a converter and recovering valuable metal in the ore by reducing the ore, a large amount of heating or Requires reduction energy. further,
In the operation of the converter, a large amount of ore is required to improve productivity.
Moreover, it is necessary to supply it into the converter at high speed to heat and reduce it. For this reason, the energy supply in the converter needs to be a higher density and a large amount of energy supply.

As the energy source, carbonaceous materials such as coke and coal are generally used, and the method of obtaining the required energy by the heat of oxidation reaction of these carbonaceous materials is CA.
MP-ISIJ vol. 7 (1988) -136,1.
It is shown at 37. However, the primary combustion of coal or coke, that is, the reaction of C + (1/2) O ₂ → CO ₂ alone is economically disadvantageous because it requires the use of a very large amount of carbonaceous material.

Therefore, attention has been paid to a method of further burning CO gas generated by the primary combustion of carbonaceous material to CO ₂ , that is, a secondary combustion technique. According to this method
Compared to the primary combustion reaction, several times as much energy can be obtained without increasing the amount of carbonaceous material used, which makes it possible to dramatically improve the productivity of the converter.

Further, it is known that the increase in secondary combustion efficiency also causes a decrease in dust generation rate as a secondary effect. The following techniques are conventionally known as techniques for improving the secondary combustion efficiency having such effects. Raising the height of the upper blowing lance (hereinafter abbreviated as the lance height) Supplying oxygen for secondary combustion from the upper blowing lance or the tuyere of the furnace wall The above and the above are disclosed in JP-A-1-219116. The lance height is set to 3 m or more, and a high secondary combustion rate is obtained by optimizing the nozzle inclination angle of the circular auxiliary hole and the flow distribution ratio with the main hole.

A method of supplying secondary combustion oxygen from the tuyere of the furnace wall is disclosed in JP-A-64-39311, in which oxygen injection by the main lance is softened (vertical oxygen jet vertical). Slow down the direction speed)
By supplying secondary combustion oxygen from the tuyere of the furnace wall, the secondary combustion ratio has been improved. Further, as a method for more effectively utilizing the high-density secondary combustion energy obtained by the above method, a method of immersing an upper blowing lance in a molten slag layer is disclosed in JP-A-1-255613.

This method is intended to produce a large amount of molten slag during the smelting reduction operation and utilize it as a heat medium for molten steel.

[0008]

However, as disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-219116,
When operating with the lance height increased, the heat deposition efficiency decreases in proportion to the increase in the distance between the molten metal bath and the secondary combustion zone, and as a result, the exhaust gas temperature rises, causing the amount of refractory melt loss. The result was an increase in the number, which hindered stable operation.

Further, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 64-39311, the use of the side wall tuyeres in the furnace wall does not cause the above problems, but the tuyeres are installed in the furnace wall. Along with this, there have been problems that the burden of equipment costs is increased and the amount of refractory material in the furnace near the tuyere is increased. Further, as disclosed in JP-A-1-255613, the method of immersing the upper blowing lance in the slag layer reduces the distance between the surface of the molten metal bath and the tip of the lance, especially at the beginning of operation. Not only a high secondary combustion rate cannot be obtained, but also the dust generation rate increases.

Further, since the lance is immersed in the molten slag layer, the risk of melting damage at the tip of the lance increases. Therefore, one of the inventors of the present invention has previously achieved a high secondary combustion rate and a high heat deposition efficiency by a combination of improving the shape of the lance nozzle and optimizing the operating conditions, as a means for solving such a problem. Proposing a method.

That is, as disclosed in Japanese Patent Application No. 4-24564, the central hole of the upper blowing lance is eliminated and the vertical flow velocity V of the upper blowing oxygen jet on the surface of the molten metal bath.
_By combining _{Z with} the appropriateness, the secondary combustion rate and heat transfer efficiency were improved, and the dust generation rate was suppressed. However, there is a strong demand for further improvement in productivity in the converter operation, and even with the technology disclosed and applied in Japanese Patent Application No. 4-24564, the smelting reduction productivity of chromium ore, which is the ore to be reduced, was low.

As one of the improvement methods, an attempt was made to lower the lance height and bring the molten metal and the secondary combustion zone closer to each other with the aim of increasing the heat deposition efficiency, but the secondary combustion rate decreased and dust was generated. The speed has increased significantly. This also resulted in V _Z deviating from the appropriate value. In order to solve the above-mentioned problems, the present invention improves the heat generation efficiency with a lower lance height than the conventional one, and at the same time improves the secondary combustion rate and reduces the dust generation rate, the shape and operating conditions of the lance nozzle. To find a combination of optimizations.

[0013]

[Means for Solving the Problems] The present inventors have conducted various experiments and studies in order to achieve the above object. As a result, in a converter-type smelting reduction furnace having a top-bottom blowing function, the chromium-containing raw material and the carbonaceous material are supplied from the top of the furnace to the iron-containing raw material charged in the furnace while oxygen is supplied from the top-blowing lance. In the smelting reduction, the upper blowing lance has a rectangular oxygen ejection opening hole having a long-short side ratio k of 1.3 or more in the periphery of the tip of the lance and has a central hole. Using a non-blown top-blown lance, the vertical velocity V _Z of the top-blown oxygen jet on the surface of the molten metal bath shown by the equation 2 is 30 m / s or more, 7
It has been found that the above-mentioned object can be achieved by operating while adjusting the top-blowing oxygen flow rate and the top-blowing lance height so as to be 0 m / s or less.

[0014]

[Equation 2]

Here, n is the number of nozzles of the upper blowing lance (-), d is the diameter of a circle equal to the nozzle (rectangular opening) cross-sectional area (m), k is the ratio of the long side to the short side of the nozzle (rectangular opening) ( -) H: Height of top-blowing lance (m), that is, the distance from the surface of the stationary molten metal bath to the tip of the top-blowing lance Q: Top-blowing oxygen flow rate (Nm ³ / s) Θ: Nozzle tilt angle with respect to the center line of the top-blowing lance (Ra
d) The present invention also proposes claim 2 as a desirable oxygen top blowing lance.

[0016]

[Function] In the process of recovering valuable metals for the smelting reduction of ore raw materials into molten metal, the use of a converter with a top-bottom blowing function allows a large amount of oxygen gas to be supplied from both top-bottom blowing to achieve high production. It is effective in that it not only enables smelting reduction due to its properties, but also enhances the reduction reaction rate of valuable metal oxides in slag by vigorous stirring by bottom-blown gas and efficiently recovers them in the molten metal bath. .

The technique, which is the essence of the present invention, uses an upper blowing lance of a rectangular nozzle having no central hole, and the molten metal bath surface is changed according to the height of the molten metal bath surface which is constantly changing during the smelting reduction operation. In order to control the vertical gas flow velocity of the top-blown oxygen jet in the appropriate range, the lance height and the top-blown oxygen flow rate are adjusted to achieve both high heat transfer efficiency and improvement of secondary combustion. The present invention provides a method for operating a smelting reduction furnace that also realizes suppression of dust generation rate.

One of the essential requirements of the present invention is the idea of using a top blowing lance of a rectangular nozzle without a central hole, compared to a circular nozzle without a central hole and a lance with a central hole. With the same lance height, the vertical gas flow velocity of the top-blown oxygen jet on the molten metal bath surface can be reduced.
That is, it is based on the discovery of the fact that the top-blown oxygen jet can be soft-blown.

More specifically, from an extensive investigation of the flow velocity of the oxygen jet that causes secondary combustion and the flame expansion range,
In the case of a fully developed turbulent flame, the length of the flame should not be extended even if the flow velocity of the oxygen jet is increased more than necessary.
This is also due to the discovery of the fact that the flame expansion range at the same gas flow rate from a nozzle having the same cross-sectional area can be made larger in the vertically elongated rectangular nozzle.

That is, in order to make the flame expansion range as wide as possible for the same secondary oxygen supply amount, it is not necessary to make the oxygen jet flow velocity higher than the limit value at which the turbulent flame sufficiently develops. Rather, we discovered the fact that using a vertically long rectangular nozzle to evenly inject an oxygen jet over the widest possible area on the steel bath in a converter improves secondary combustion efficiency. This is because it was also found that the expansion of the secondary combustion zone due to blowing increases the heat transfer efficiency from the secondary combustion zone to the steel bath, and improves the heat deposition efficiency under the same secondary combustion rate.

In order to execute this, as shown in FIG.
Based on the finding that it is optimal to use a top blowing lance without a central hole, which has a vertically elongated rectangular nozzle that allows a wide distribution angle of secondary oxygen jet injection along the curvature of the lance tip. . The effect of making the oxygen jet soft-blowed by this was that, at the same lance height, in addition to the improvement of the secondary combustion rate, it effectively acted on the improvement of the heat generation efficiency and the suppression of the dust generation rate.

The second essential requirement of the present invention, that is, the optimization of the upper blowing condition, is based on the following reason. During the operation of the smelting reduction furnace, carbonaceous materials such as ore raw material, coke, and coal are continuously charged into the furnace, and the ore raw material is recovered in the molten metal bath, so that the molten metal amount increases. Therefore, when the lance height during the smelting reduction is fixed and the operation is performed, the substantial lance height decreases as the operation progresses. As a result, since the top blowing condition is hard blow due to the decrease in the lance height, it becomes difficult to maintain a high secondary combustion rate and suppress the dust generation rate.

Therefore, it is important to prevent the hard blow by adjusting the height of the lance and the flow rate of the top-blown oxygen according to the progress of the smelting reduction. Regarding compatibility between high secondary combustion rate and high heat deposition efficiency, optimization of top-blowing conditions such as top-blowing oxygen flow rate and lance height was examined using a 5 t capacity converter shown in FIG. First, regarding the shape of the upper blowing lance, nozzles are provided only in the peripheral portion shown in FIG. 6, and the upper blowing lance of a rectangular nozzle having no central hole and the upper blowing lance of a circular nozzle having no central hole shown in FIG. A smelting reduction operation of chromium ore was carried out by using a nozzle in the peripheral portion shown in 8 and an upper blowing lance having a central hole. However, in this case,
The number of nozzles and the nozzle diameter of each top blowing lance were the same. The rectangular nozzle has the same cross-sectional area as the circular nozzle.

As a result, as shown in FIG. 2, it was confirmed that the secondary combustion efficiency was most improved by using the upper blowing lance of the rectangular nozzle having no central hole at the same lance height. This means that, as described above, in order to make the expansion range of the flame as wide as possible for the same secondary oxygen supply amount, the oxygen jet flow velocity should be set higher than the limit value at which the turbulent flame sufficiently develops, In other words, the fact that the uniform injection of oxygen jet over the widest possible area on the steel bath in the converter improves the secondary combustion efficiency represents the discovery itself.

Moreover, as shown in FIG. 3, it was found that the heat transfer efficiency of the secondary combustion heat to the molten metal bath at the same secondary combustion rate was also most improved. It was presumed that even in the operation with the same secondary combustion rate, the secondary combustion occurring in the steel bath in the converter as wide as possible would increase the heat deposition efficiency to the molten steel. Further, as shown in FIG. 4, it was found that the dust generation rate also decreases at the same lance height due to the effect of soft blowing by eliminating the central hole.

In FIGS. 2 to 4, ⊚ indicates a rectangular nozzle without a central hole, ● indicates a circular nozzle without a central hole, and ∘ indicates a nozzle with a central hole. Next, the optimization of the top-blowing lance shape, the top-blowing oxygen flow rate, the flow velocity, the lance height, and other top-blowing operating conditions were examined using the top-blowing lance of the rectangular nozzle having no central hole shown in FIG.

As a result, as shown in FIG. 5, the vertical flow velocity V _Z value of the upward-blown oxygen jet on the molten metal bath surface calculated by the equation 3 becomes 30 m / s or more and 70 m / s or less. It was found that by adjusting the top blowing operation conditions, it is possible to achieve both a high secondary combustion rate and a high heat deposition efficiency.

[0028]

[Equation 3]

However, n: number of nozzles of the upper blowing lance (-) d: diameter of a circle equal to the cross-sectional area of the nozzle (rectangular opening hole) (m) k: ratio of the long side to the short side of the nozzle (rectangular opening hole) ( -) H: Height of top-blowing lance (m), that is, the distance from the surface of the stationary molten metal bath to the tip of the top-blowing lance Q: Top-blowing oxygen flow rate (Nm ³ / s) Θ: Nozzle tilt angle with respect to the center line of the top-blowing lance (Ra
d) The long / short side ratio k of the nozzle will be described in more detail. As shown in FIG. 9, the nozzle has a rectangular cross-sectional shape, and the long side length is a and the short side length is b. When
The value of k = a / b is shown.

A desirable nozzle tilt angle with respect to the center line of the upper blowing lance is π / 18 to 2π / 9 rad (where π
Is the pi). If the nozzle tilt angle is less than π / 18 rad, it is not preferable from the viewpoint of secondary combustion efficiency, while if it is more than 2π / 9 rad, it is not preferable from the viewpoint of heat deposition efficiency. Also, in this formula, the number 4

[0031]

[Equation 4]

Represents the vertical velocity of the oxygen jet when a circular nozzle is used, and the coefficient [(k + 1) / (1.77
k)] represents the effect of soft blowing when the nozzle shape is changed from a circular shape to a rectangular shape. That is, in the above equation, in the case of nozzles having the same cross-sectional area, V increases as the ratio of the long side length to the short side length of the nozzle-shaped rectangle increases.
It shows that _Z becomes small, that is, soft blow.

When a rectangular nozzle and a circular nozzle having the same cross-sectional area are compared with each other, in order to reduce V _Z , that is, to realize soft blowing, the ratio k between the long side length and the short side length of the rectangle is 1. It is also a result of conducting various experiments and research that the effect of soft-blowing is not effective unless it is 0.3 or more. That is, including the above, from FIG. 5, by adjusting the upper blowing operation conditions such that the V _Z value during smelting reduction is 30 m / s or more and 70 m / s or less, a high secondary combustion rate and high heat deposition efficiency can be obtained. It can be seen that it can be achieved together, and the operation that is advantageous in terms of thermal energy can be realized.

The above findings show that the V _Z value is calculated in accordance with the elimination of the central hole of the upper blowing lance, the rectangular nozzle tip and the rise of the molten metal bath surface accompanying the increase of the molten metal amount during the operation. It is shown that by adjusting the lance height and the like based on the above, it is possible to realize soft blowing under the upper blowing conditions in general, which is an essential requirement in the present invention.

[0035]

【Example】

[Example] An example of the present invention carried out by using a converter having a top and bottom blowing function of a furnace capacity of 5 ton shown in FIG. 1 will be described below. In FIG. 1, 1 is a converter main body, 2 is a bottom blowing tuyere, 3 is a molten metal bath, 4 is a molten slag layer, 5 is lump coke, 6 is a top blowing lance, 7 is a chrome ore, coke, etc. It is a shooter on the furnace for charging auxiliary materials. The top blowing lance 6 is a rectangular nozzle without a central hole shown in FIG.
2, the one with θ = π / 12 rad was used.

In the operation, hot metal having a chemical composition shown in Table 1 which had been dephosphorized in advance was charged into the converter body 1, and then pure oxygen was upwardly blown by the bottom blowing tuyere 2 and the upper blowing lance 6 to produce coke. The temperature of molten metal bath is 155 when put into the furnace.
Blowing was performed for about 8 minutes until the temperature reached 0 ° C.

[0037]

[Table 1]

Subsequently, the agglomerated coke was 24 kg / min by the furnace shooter 7, and the agglomerated chrome ore was adjusted to 25 at a molten metal bath temperature of 1550 ± 20 ° C.
The addition was adjusted within the charging speed range of -60 kg / min.
Further, lump lime was added by the shooter 7 on the furnace so that the slag basicity became 1.5.

The compositions of the lump coke and chrome ore used are shown in Tables 2 and 3.

[0040]

[Table 2]

[0041]

[Table 3]

Further, in order to maintain the lance height during operation at 1.0 m from the molten metal bath surface, the lance was gradually raised in consideration of the amount of molten metal increased by the reduction of the chromium ore. When the lance height is maintained at 1.0 m, the value of V _Z is 30.1 (m / s), which is in the range of 30 m / s or more and 70 m / s or less.

During the operation, the temperature of the molten metal bath was measured by using a sublance, and the charging rate of the chromium ore was adjusted on the basis of the measured value as described above so that the temperature of the molten metal bath was 1.
The operation was performed so as to be 550 ± 20 ° C. Chromium ore is added for about 60 minutes, and after that, finish reduction for reducing and recovering the chromium remaining in the slag without adding the chromium ore is performed at a molten metal bath temperature of 1550 ± 20 ° C. for about 1 minute.
It was carried out for 0 minutes.

The results of this operation are shown in Table 4.

[0045]

[Table 4]

As is clear from Table 4, chromium in the charged chromium ore was recovered in the metal bath with a high yield of 97.0%, and the remaining 3.0% was slag, dust, stippling metal, etc. It was due to the escape to the outside of the furnace.
Further, when the melting loss amount of the converter refractory was measured before and after the operation, the average value of the furnace bottom and the furnace side was 1.6 mm, and 2.
It was 3 mm. [Comparative Example] The same equipment and operating method as in Example were used, but the top blowing lance used had a nozzle arranged at the center of the lance tip as shown in FIG. 8 (Comparative Example 2).
As shown in FIG. 7, a circular nozzle type (Comparative Example 1) in which the central hole was eliminated was used.

The operation results in this case are also shown in Table 4 as in the example.
Are summarized in. As is clear from Table 4, depending on the presence or absence of the center hole of the upper blowing lance and the difference in the nozzle shape,
The addition amount of chromium ore and chromium yield are different. That is, the central hole of the upper blowing lance is eliminated as in the embodiment,
Moreover, by making the nozzle rectangular, the top-blown oxygen jet is soft-blown, and as a result, when the molten metal bath temperature is kept constant, the secondary combustion rate in the furnace improves and It is understood that not only the amount of chromium ore input increases, but also the amount of dust and stippling that escape to the outside of the furnace decrease, improving the chromium yield and steel production yield.

Further, the melting loss of the converter refractory in the comparative example is
The average value of the furnace bottom and the furnace side is 1.6 mm, and the furnace top is 2.3 mm.
Was the same as the example. As described above, in the case of the example, as a result of eliminating the center hole with the upper blowing lance and making the nozzle rectangular, the melting loss amount of the refractory material is different from the comparative example even if the secondary combustion rate in the furnace is improved. The reason for this is that the top-blown oxygen jet is dispersed relatively uniformly, and the heat generated by the secondary combustion is effectively transferred to the molten metal bath and the slag layer.

In the examples and comparative examples, the flow rate of oxygen blown from the bottom tuyere is about 0.083 Nm ³ / s.
And certain conditions. From the above, from the viewpoint of soft-blowing the top-blown oxygen gas jet, elimination of the central hole and rectangularization of the nozzle are important. Not only can the amount of chrome ore be increased, the heat absorption efficiency of the secondary combustion heat can be improved, so that the amount of refractory melting can be suppressed, and the heat absorption efficiency of the secondary combustion heat can be improved. Therefore, the amount of refractory melt loss can be suppressed.

In addition, it is possible to reduce the amount of dust and stippling that escape to the outside of the furnace, so that it is possible to carry out blowing with a high chromium yield.

[0051]

According to the present invention, by using the upper blowing lance of a rectangular nozzle having no central hole, and adjusting the lance height in accordance with the molten metal bath surface level which is constantly changing during the operation, the converter furnace is adjusted. It becomes possible to carry out the smelting reduction operation of chromium ore with high productivity and high chromium yield while suppressing the melting damage of the refractory.

Although the description has been made mainly on the chromium ore, the technique of the present invention also applies to iron ore, manganese ore, nickel ore and other carbon-reducible ores, and their agglomerated ores and preliminary reduced ores. Can be applied effectively.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a 5-ton scale converter equipment used in the practice of the present invention.

FIG. 2 is a characteristic diagram showing the influence of the presence or absence of a center hole of an upper blowing lance on the secondary combustion rate in the furnace in the smelting reduction of chromium ore.

FIG. 3 is a comparative diagram showing the relationship between the average secondary combustion rate and heat deposition efficiency during smelting reduction of chromium ore.

FIG. 4 is a comparison diagram of dust generation rates in smelting reduction of chromium ore.

FIG. 5 is a characteristic diagram showing the influence of the vertical flow velocity V _Z of the upward-blown oxygen jet on the surface of molten iron on the secondary burning rate and heat deposition efficiency during smelting reduction of chromium ore.

FIG. 6 is a schematic diagram of an upper blowing lance used for carrying out the present invention.

FIG. 7 is a schematic diagram of an upper blowing lance used in a comparative example of the present invention.

FIG. 8 is a schematic diagram of an upper blowing lance used in a comparative example of the present invention.

FIG. 9 is a view for explaining a long-side ratio and a rectangular cross section of a nozzle.

[Explanation of symbols]

1 Converter Main Body 2 Bottom Blowing Tuyere 3 Molten Metal Bath 4 Molten Slag Layer 5 Bulk Coke 6 Top Blowing Lance 7 Top Furnace Shooter θ Nozzle Inclination (ra
d)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C21C 5/28 C21C 5/30 C21C 5/46 101

Claims (2)

(57) [Claims] 1. In a converter-type smelting reduction furnace having a top-bottom blowing function, a chromium-containing raw material and a carbonaceous material are fed from above the furnace to an iron-containing raw material charged in the furnace while oxygen is fed from a top-blowing lance.
When supplying and smelting reduction ,
The surface of the molten metal bath shown in Formula 1 has a rectangular oxygen ejection opening hole with a long- to- short side ratio k of 1.3 or more in the periphery of the tip of the lance, and uses an upper blowing lance without a center hole. Converter type that is operated while adjusting the top-blowing oxygen flow rate and the top-blowing lance height so that the vertical flow velocity V _Z of the top-blowing oxygen jet at 30 m / s or more and 70 m / s or less Operation method of smelting reduction furnace. [Equation 1] However, n: number of nozzles of upper blowing lance (-) d: diameter of circle equal to nozzle (rectangular opening hole) cross-sectional area (m) k: long-side ratio (-) H of nozzle (rectangular opening hole) cross-section : Top-blowing lance height (m), that is, the distance from the surface of the stationary molten metal bath to the top-blowing lance tip Q: Top-blowing oxygen flow rate (Nm ³ / s) Θ: Nozzle tilt angle (ra with respect to the center line of the top-blowing lance
d) 2. A rectangular opening hole having a long-to-short side ratio k of 1.3 or more is provided in the peripheral portion of the tip of the lance, and a nozzle inclination angle θ with respect to the center line of the lance is π / 18 to 2π / 9 rad (where π).
Oxygen <br/> on lance, characterized in that no in pi), and center hole.