JPH08176631A - Operation of vertical type metal smelting reduction furnace - Google Patents

Abstract

PURPOSE: To stably operate a vertical type metal smelting reduction furnace in the high productivity by blowing oxygen-containing hot blast from plural tuyeres at the lower part of a packing layer of solid reduction materials so as to deflect at a fixed angle to the radial direction at the fitting height of the tuyeres. CONSTITUTION: Cabonaceous material 3 is charged as the solid reduction material from the furnace top of the vertical type molten metal smelting reduction furnace 1 to form the packing layer 6 of the carbonaceous material in the furnace. Powdery and granular ore raw material 9 containing metallic oxide and flux 8 stored in raw material hopper group 14 are injected together with the oxygen-containing hot blast 2 to this packing layer 6 from plural tuyeres 4, 5 at the lower part of the furnace. By this method, the carbonaceous material 3 is burnt in raceways 7 formed in the packing layer 6 and the smelting reduction is executed to the metallic oxide with generated heat and CO gas and the obtd. metal is tapped off from an iron tapping hole 12. In the above operational method, the blowing of the hot blast into the furnace is deflected at the fixed angle to the radial direction of the furnace at the fitting height of the tuyeres, desirably, in the range of 10-45 deg. angle. By this method, the circulation of fused material, grains, etc., in the furnace and blow-off of gas, etc., are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a vertical molten metal reducing furnace having a packed bed of a carbon-based solid reducing agent,
In particular, using granular ores and / or dust as raw materials,
The present invention relates to a method for producing the molten metal more efficiently than the metal oxides contained therein and, at the same time, reducing the phosphorus content in the molten metal.

[0002]

2. Description of the Related Art Generally, in order to produce a large amount of molten metal such as pig iron, a blast furnace which requires a lumpy raw material is often used. However, due to the recent circumstances of raw materials, the number of ore raw materials containing iron oxide or various metal oxides is decreasing in the form of lumps and increasing in the form of powder or small grains, and the tendency is increasing. It is considered.

On the other hand, as a method for producing molten metal by directly using powdery granular ore, a fluidized bed type furnace is used to pre-reduce powdery granular ore, and the pre-reduced ore is melted in an electric furnace, a converter or the like. The method of smelting and reducing is generally used. However, in this method as well, the pre-reduced ore is often used by being agglomerated by adding a binder and the like, which not only requires extra processing cost and energy for agglomeration, but also agglomerates. If additional firing is required after compounding, in addition to the firing cost, N
O _X, the cost of prevention of SO _X and dust has the disadvantage becomes great. Further, a method of smelting and reducing the above-mentioned pre-reduction ore in a granular form by using an arc furnace, a plasma furnace or a pure oxygen furnace is also proposed, but the power consumption becomes enormous. There are problems such as restrictions on conditions, and it has not been realized yet. Therefore, the applicant of the present invention has previously disclosed JP-A-57-198205 and JP-A-5-198205.
The so-called vertical molten metal reduction furnace disclosed in many other publications such as 8-77548 has been developed and is being put into practical use.

As shown in FIG. 1, the furnace has an upper tuyere 4
And the lower tuyeres 5 are provided, and a carbon-based solid reducing agent is supplied from a carbonaceous material supply device (not shown) above the furnace to form a packed bed 6 in the furnace. The heat source is supplied with high-temperature air 2 from a high-temperature air blower (not shown), and the high-temperature air 2 is distributed by a distributor to a plurality of tuyere 4, 5 arranged in upper and lower two stages. The raw material powdered ore and the flux 8 from the flux supply device are blown into the furnace from the upper tuyeres 4 through the powdered material transport pipe 10 by the powdered material blowing device, and the generated molten metal and slag are discharged. Piggy 1
Emitted from 2. Further, the gas 13 discharged from the vertical molten metal reduction furnace 1 is processed by the exhaust gas processing device. This furnace does not use expensive electric power or strong coking coal, uses relatively inexpensive weak cohesive or non-cohesive coal, and effectively reduces the reducing gas discharged from the furnace. Since it has the advantage of being used for the preliminary reduction of the above, it can be expected as a molten metal production apparatus in the future, where the increase in energy cost is more and more dangerous.

On the other hand, at present, in order to obtain low-phosphorus pig iron or low-phosphorus steel, dephosphorization treatment is carried out in the so-called hot metal pretreatment step or steelmaking step, and ultra-low phosphorus coke is generally used in the production of hot metal. Target. In the hot metal manufacturing method using a blast furnace, the phosphorus content in coke is almost 1%.
Since 00% is transferred to the hot metal, coke with a low phosphorus content must be used in the production of low phosphorus hot metal, and powder containing FeO or Fe ₂ O ₃ should be added to the hot metal according to the required phosphorus component. This is because it is necessary to perform the blowing and the hot metal dephosphorization treatment. Further, when coke is used as carbonaceous material in the steelmaking process (melt reduction of Cr ore), the phosphorus content in the coke is transferred to the steel, which necessitates further dephosphorization and treatment for dephosphorization. This is because installation of equipment is required separately, and an electrolysis method aiming at low phosphorus steel is also proposed, but this method results in enormous energy cost and is not suitable for mass production.

However, the dephosphorization treatment in the hot metal pretreatment step or the like puts a burden on the next step, ie, the hot metal dephosphorization treatment outside the furnace or the converter smelting, which is uneconomical as a total process, or the above-mentioned burden. Even when a low phosphorus coke is used in order to avoid the problem, the low phosphorus coke (manufacturing method is described in JP-A-52-
However, there is a problem in that it is economically disadvantageous because it is expensive. Therefore, as a method for inexpensively mass-producing low phosphorus pigs having a phosphorus content of 0.01% by weight or less without using a carbonaceous material such as low phosphorus coke, the applicant of the present invention discloses Japanese Patent Application Laid-Open No. 57-198205. Publication, JP-A-5
As disclosed in Japanese Patent Application Laid-Open No. 9527 and Japanese Patent Application Laid-Open No. 5-247549, a method of utilizing the vertical molten metal reduction furnace has been proposed. This is because the vertical molten metal reduction furnace is different from the blast furnace in that a so-called softening cohesive zone is not formed in the furnace and phosphorus is not circulated in the furnace, which is preferable for the production of low phosphorus pig iron. That is, as disclosed in the above publication, vaporization and dephosphorization can be performed by adjusting the temperature in the furnace to a high temperature.

As described above, the vertical molten metal reduction furnace proposed by the present applicant not only solves the problem of exhaustion of future energy sources, but is also suitable for the production of molten metal having a low phosphorus content. there were. However, the refining methods using this furnace that have been proposed so far have not been completely established yet, and some problems remain. For example, in the case of dephosphorization, in the case where the vertical molten metal reduction furnace is provided with only a pair of upper and lower tuyere and blows air from there,
As shown in FIGS. 2 (a) and 3 (a), a wall 9 of molten slag is formed around the raceway 7 formed at the tuyere tip,
Since the coke descends only within the area covered by the wall 9 (raceway side), the coke between the upper and lower tuyeres passes through a high temperature area of 1800 ° C. or higher near the upper and lower tuyeres, It is vaporized and dephosphorized in the region. However, since the tuyere of the furnace is usually provided at a plurality of locations in the circumferential direction, even if the depth of the raceway 7 is 40% of the furnace diameter, as shown in FIG. Since the coke particle swirling regions 11 formed in the upper part overlap each other, the molten slag wall 9 is not formed around the raceway 7 as in the case of using only the pair of upper and lower tuyere, and the furnace is All of the coke particles descending inside do not necessarily pass through the high temperature region of 1800 ° C. or higher. That is, even if the vertical molten metal reduction furnace 1 is used, it is not possible to stably vaporize and dephosphorize in any case. In addition, since a part of the powdery ore and / or dust containing the metal oxide blown from the upper tuyeres turns around the raceway 7 together with the coke particles, and the melt exists above the raceway 7, The melt may absorb vaporized phosphorus. In addition to the dephosphorization, the blown ore raw material 9 and the powder of the flux 8 are melted in the space of the raceway 7 formed in front of the upper tuyeres 4, and while the melt is dropped to the lower tuyeres 5. The molten metal and slag are retained in the hearth as molten metal and slag, but the refining area of this furnace is limited to the raceway 7 space and the area where the molten material drops below it, and the raceway occupies the horizontal cross section of the furnace. There is also a problem that productivity cannot be improved unless the area of 7 regions is increased. In addition, as shown in Japanese Patent Application Laid-Open No. 4-225756, when the depth of the raceway 7 exceeds 40% of the furnace diameter during operation, blow-through of the gas in the furnace may occur and the gas was blown in. There is also a problem that the powder of the ore raw material 9 and the flux 8 is not reduced as it is and jumps out of the furnace.

[0008]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention prevents the melt, dust, coke, etc. from circulating in the furnace, blows out the gas in the furnace, and prevents coke particles from falling. It is an object of the present invention to provide a method for operating a vertical molten metal reduction furnace which promotes vaporization and dephosphorization by passing all around the upper tuyeres and has a stable gas flow distribution and high productivity.

[0009]

In order to achieve the above-mentioned object, the inventor has earnestly studied the size and shape of the so-called raceway at the tuyere, and has come up with the present invention.
That is, the present invention, a packed bed of carbon-based solid reducing agent is formed, while blowing oxygen-containing hot air from a plurality of tuyere arranged in the lower part of the packed bed, powdery ore containing metal oxides And / or dust is blown into the furnace to melt and reduce the metal oxide to produce a molten metal. In the operating method of a vertical molten metal reduction furnace, the blowing of the oxygen-containing hot air into the furnace is performed by tuyere attachment. A vertical molten metal reduction furnace operating method is characterized in that the metal oxide is melt-reduced by being deflected at a certain angle with respect to the radial direction of the furnace. Further, the present invention is a method for operating a vertical molten metal reduction furnace, wherein the constant angle is in the range of 10 to 45 degrees, and further, hot air blowing is performed from at least two locations on the circumference of the furnace. It is also a method of operating a vertical molten metal reduction furnace characterized by being performed.

In this case, the raw material containing the metal oxide is
Other than the above, sintered ore powder or slag powder may be used. The hot air is blown into two or more locations for the purpose of the present invention, but is preferably four locations from the viewpoint of effectively utilizing the furnace internal volume.

[0011]

In the present invention, the packed bed of the carbon-based solid reducing agent is formed, and the oxygen-containing hot air is blown from the plurality of tuyere arranged at the lower part of the packed bed, and the granular ore containing the metal oxide. In a method for operating a vertical molten metal reduction furnace in which a metal and / or dust is blown into the furnace to melt and reduce the metal oxide to produce molten metal, the blowing of the oxygen-containing hot air into the furnace is performed by tuyere. The metal oxide is melted and reduced by deflecting it at a fixed height with respect to the radial direction of the furnace at the installation height, so that the periphery of the raceway formed at the tuyere is partitioned by the wall of the molten slag. become. As a result, even in a vertical molten metal reduction furnace with a structure in which air is blown from multiple locations in the circumferential direction of the furnace, an independent high temperature region can be secured for each raceway, and vaporization and dephosphorization from coke particles can be achieved. Not only can it be performed stably, but the stabilization of the gas flow distribution in the furnace, the so-called rise of blow-through limit, etc. can be achieved.
Further, in the present invention, the above-mentioned constant angle is set within the range of 10 to 45 degrees, and further, hot air blowing is performed from at least two locations on the circumference of the furnace, so the above-mentioned effect is further ensured. , Productivity has also improved.

The contents of the present invention will be supplemented below with reference to FIGS. First, regarding vaporization and dephosphorization from coke particles, as shown in FIG. 3 (c) in the practice of the present invention, 1800 surrounded by a wall of molten slag around raceway 7 was formed.
A high temperature region above ℃ can be created. Then, all coke particles descending in the furnace pass through the high temperature region formed in any of the circumferential direction of the furnace, and therefore vaporization dephosphorization is performed by the following reaction. The high temperature region is generally within 500 mm of the raceway 7 space and its periphery.

The reaction in the raceway part is as follows: 2Ca ₃ P ₂ O ₈ (in coke) + 5C → 3CaO + 2P + 5CO (1) When SiO ₂ is present, the reduction of calcium phosphate in the coke by the gas and the solid reducing agent It becomes easier according to the following formula. _{2Ca 3 P 2 O 8 + 3SiO} 2 + 10C → 3Ca 2 SiO 4 + 4P + 10CO ... (2) 2Ca 3 P 2 O 8 + 3SiO 2 + 10CO → 3Ca 2 SiO 4 + 4P + 10CO 2 ... (3) Therefore, comprises a metal oxide from the top tuyeres upon blown raw material, to increase the SiO ₂ concentration in the raw material, to increase the SiO ₂ concentration in the upper tuyere, (2), to accelerate the reaction of (3), which tends to occur more dephosphorization reaction . Above (1)
The phosphorus reduced by the formula (3) rises in the furnace together with the gas in the furnace, but as the temperature decreases, part of it adheres to dust and the like, and part of it becomes compounds such as PN, PS, and PO. Get out of the furnace top. That is, since the phosphorus in the coke is reduced in the vicinity of the raceway as described above, the coke existing below the raceway 7 has a reduced phosphorus concentration.

On the other hand, phosphorus contained in the metal oxide raw material is also partially removed by the following reaction. 2Fe ₃ (PO ₄ ) ₂ + 16CO → 3Fe ₂ P + P + 16CO ₂ (4) The metal oxide raw material blown from the tuyere melts in the vicinity of the raceway and is separated from a part of phosphorus by the reaction of (4). Then, the gaseous phosphorus rises with the gas in the furnace, and the generated molten metal is reduced while dropping between the cokes to become pig iron. As described above, since the phosphorus concentration in the coke existing in the lower part of the furnace is low, the amount of the molten metal absorbing phosphorus in the coke during the dropping is small, and the phosphorus concentration in the pig iron is also low. Further, when the temperature in the area within 500 mm around the raceway is 1800 ° C. or higher, the temperature in the vicinity of the raceway where phosphorus and metal oxide coexist is sufficiently high, so that the above-mentioned gaseous phosphorus rapidly rises in the furnace, Further, since the molten metal also has a low viscosity, the dropping is quick and the gaseous phosphorus is hardly trapped in the molten metal.

The finer the particle size of the metal oxide raw material to be blown, the faster the heat transfer to the center of each particle, so the temperature rises in a short time, and the reaction in (4) above becomes smoother. To be done. Further, since the viscosity becomes smaller as the temperature becomes higher, the coexistence time of the above-mentioned gaseous phosphorus and molten metal becomes shorter,
The phosphorus concentration in the pig iron decreases. Further, in the vicinity of the raceway, the blown metal oxide raw material is melted, and the endothermic reaction is reduced, so that the temperature around it is lowered. The concentration of phosphorus in the hot metal can be reduced by using a metal oxide raw material that has a small amount of impurities as blown in to reduce the amount of heat that is wasted to raise the temperature of the impurities and by using a metal oxide raw material that has a small endothermic amount. It is also possible to accelerate the decrease of

Next, a phenomenon other than vaporization and dephosphorization will be described. In the conventional multi-tuyere raceway, the tuyere was attached toward the central axis of the furnace. Therefore, when the gas flow rate was increased. As shown in FIGS. 2 (b) and 3 (b), it interferes with the raceway formed by other tuyere at the center of the furnace and is likely to cause blow-through of the gas in the furnace at the center of the furnace. However, in the present invention, as shown in FIGS. 2 (c) and 3 (c), the walls of the molten slag eliminate interference between raceways formed by other tuyere, and the blow-through condition is eased. become. Also, since it became possible to secure multiple raceways of stable size and shape, the gas flow distribution in the furnace became constant, that is, the lower tuyeres gas reached the upper tuyeres directly, An increase in the temperature of the molten metal in the furnace, and thus an increase in the production amount, can be achieved.

Finally, suitable conditions for carrying out the method for operating a vertical molten metal reduction furnace according to the present invention will be described.
Since the point of the present invention is to change the hot air blowing direction into the furnace to form independent high temperature regions surrounded by the wall of the molten slag, it is preferable that adjacent raceways do not contact each other. It is a condition. To do this, the diameter of the furnace (L) and the depth of the raceway (D
The relation with _r ) must satisfy the following formula.

L- (2 × D _r )> N × π × √D _r where √D _r : width of raceway Further, as a condition that no blow-through occurs, the following two expressions must be satisfied in the same manner. Is. 0.4L ≧ D _r 22.5 × π × L ² > BV × 273 / (BT + 273) where BV: total air flow into furnace (Nm ³ / min) BT: air temperature (° C) N: blade Further, the reason why the blowing angle of the hot air is limited to 10 to 45 ° is that if the angle is 10 ° or less, the formation of the slag wall is not sufficient.
If the angle is 5 ° or more, the raceway may get caught in the furnace wall and damage the furnace wall refractory. In addition, the reason why there are two or more blowing points is that the internal volume of the furnace is wasted at one location and productivity is impaired. Furthermore, the pair of tuyeres in the upper and lower stages are always in the same direction. Is preferred.

[0019]

[Examples] In the vertical molten metal reduction furnace shown in Fig. 1, pig iron (molten metal) containing chromium from the following iron ore powder as a raw material
The manufacturing test was conducted. At that time, the operation method according to the present invention was applied, and the blowing angle was variously changed. The specifications of the smelting reduction furnace used in the test are as follows.

Furnace inner diameter: 1200 mm φ Furnace height: 4000 mm Carbonaceous material layer height: 3000 mm Number of tuyeres: 4 upper and 4 lower tiers Tubing diameter: 25 mm Upper and lower tuyer spacing: 1.0 m Raw material injection rate: 2 t / hr Also, upper tier The composition of the iron ore powder raw material blown from the tuyere is
C: 4.7% by weight, T.I. Fe: 62.4 wt% (Fe
O: 31.8% by weight), SiO ₂ : 0.8% by weight, T.I.
Cr: 6.2 wt%, MnO: 4 wt%, Al ₂ O ₃ :
1.1% by weight, other oxides: 20.6% by weight, and 0.3% by weight of slag material made of CaO and SiO _2.
It was blown at the same time under the condition of t / hr. Table 1 shows the ventilation conditions
Table 2 shows the composition of the produced pig iron and the composition of the slag.

[0021]

[Table 1]

[0022]

[Table 2]

The blast angle from each tuyere was changed in seven steps in the range of 0 to 50 degrees in the radial direction of the furnace, and the operation results of each were summarized in Table 3. According to Table 3,
The conventional blowing angle, that is, the result of 0 degree was inferior to the case of other angles, and it was confirmed that the operating method according to the present invention was effective. The state of phosphorus reduction is shown in FIG.

[0024]

[Table 3]

The air blowing angle is 5 with respect to the furnace radial direction.
If the temperature is higher than 0 degree, the furnace wall temperature of the part where the raceway seems to be in contact is higher than that of other parts, probably because the furnace wall refractory is damaged. Further, in the present example, pig iron containing chromium was produced, but the molten metal to which the present invention is applicable is not limited to pig iron, but may be non-ferrous metals such as copper, aluminum and zinc.

[0026]

As described above, according to the present invention, in the operation of a so-called vertical molten metal reduction furnace filled with a solid reducing material, the blowout limit flow velocity of the gas in the furnace is increased and the gas flow distribution is stabilized. It was possible to raise the temperature of the molten metal. Also, by focusing the fall of coke particles in the high temperature region near the tuyere, vaporization and dephosphorization from the furnace was activated, and it became possible to mass-produce low-phosphorus molten metal inexpensively and easily. .

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an outline of a furnace in which a method for operating a vertical molten metal reduction furnace according to the present invention is carried out.

FIG. 2 is a vertical cross-sectional view for explaining the internal condition of a vertical molten metal reduction furnace, in which (a) uses only a pair of upper and lower tuyere, and (b) shows a conventional multiple tuyere. , (C) show the case of a plurality of tuyere in which the present invention is implemented.

FIG. 3 is a horizontal sectional view of FIG. 2, where (a) is a case where only a pair of upper and lower tuyere is used, (b) is a conventional four-tuyere, and (c) is related to the present invention. The case of four tuyere is shown.

FIG. 4 is a diagram showing the relationship between the blowing angle from the tuyere and the phosphorus concentration in the produced pig iron.

[Explanation of symbols]

 1 Vertical molten metal reduction furnace 2 High temperature air (hot air containing oxygen) 3 Charging route for solid reducing material (carbon material or coke) 4 Upper stage tuyeres 5 Lower stage tuyeres 6 Carbon material packed layer 7 Raceway 8 Flux 9 powdered ore raw material 10 transportation route of powder and granules 11 coke particle swirl area 12 tapping hole 13 exhaust gas 14 raw material hopper group

Claims (3)

[Claims] 1. A packed bed of a carbon-based solid reducing agent is formed,
While blowing oxygen-containing hot air from a plurality of tuyere arranged in the lower part of the packed bed, and blowing powdery ore and / or dust containing metal oxide into the furnace to melt and reduce the metal oxide. In the operation method of the vertical type molten metal reduction furnace for producing molten metal, the blowing of the oxygen-containing hot air into the furnace is performed by deflecting a certain angle with respect to the radial direction of the furnace at the tuyere mounting height, and A method for operating a vertical molten metal reduction furnace, which comprises melting and reducing a metal oxide. 2. The method for operating a vertical molten metal reduction furnace according to claim 1, wherein the constant angle is in the range of 10 to 45 degrees. 3. The method for operating a vertical molten metal reduction furnace according to claim 1, wherein the hot air blowing is performed from at least two locations on the circumference of the furnace.