JP2002256325A - Pretreatment method of hot metal with low slag generation using converter type vessel - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the amount of flux used and the amount of generated slag used for preliminary treatment of de-Si and de-P by using a converter type vessel, and to increase the reaction efficiency of de-Si and de-P reactions. Provided is a method for pretreating hot metal with a small amount of slag generation using a converter type vessel that can reduce the reached Si and reached P concentrations. SOLUTION: In a pretreatment method for hot metal with a small amount of slag generated by performing a de-Si treatment and a de-P treatment using a converter type container 10, 40 to 60% by weight of slag generated in the previous pre-treatment of hot metal. Is left in the converter-type container 10, a new hot metal 16 is charged into the converter-type container 10, and the molten iron 16 is subjected to a deoxidizing treatment and a de-P-treatment by blowing and acidifying. During the P removal process, the flux 15 is added to the hot metal 16, and further, the Si removal process and the P removal process are continuously performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for removing Si (silicon) and removing P
(Phosphorus) Using a part of the slag generated when performing the treatment, the pre-treatment method of the hot metal with a small amount of slag generation using a converter type vessel that performs de-Si treatment and de-P treatment of new hot metal .

[0002]

2. Description of the Related Art Conventionally, hot metal, which is a main raw material of steelmaking, is made of Si.
(Si), S (sulfur), P (phosphorus), and other impurities, and removes these impurities in advance to remove Si, remove S, remove P
So-called pretreatment of hot metal is performed. In particular, when performing the de-Si treatment and the de-P treatment at the same time, a flux for dephosphorization such as quicklime and soda ash and gaseous oxygen for oxidizing P in the hot metal, or a solid oxidizing agent such as iron oxide, dust collection dust, and sludge are used. , Or by injecting a flux or a solid oxidant (injection) to remove Si in the hot metal preferentially into SiO ₂ and remove P at the same time as an oxide (P ₂ O ₅ ), It is captured by CaO in the generated slag and removed from the hot metal. However, in the pretreatment of such hot metal, Si can be easily removed as SiO ₂ , but the reaction efficiency of P removal is poor, and it is difficult to sufficiently reduce the ultimate P concentration. As a countermeasure against this, JP-A-62-1
As described in JP 09910 Gazette, a flux containing a slagging accelerator containing CaO as a main component is placed on the surface of hot metal, and while oxygen is blown upward from a lance, solids such as iron ore and scale are removed. A method of injecting a powder of an oxygen agent into hot metal has been used. Further, JP-A-6-287
No. 616, iron oxides 60 to 8
0% by weight of CaO-Fe ₂ O ₃ -CaF ₂ system flux containing, those of Na ₂ O ₃ were blended 3 to 10 wt%, and Inzekushon into hot metal, hot metal using a lance from above Spraying oxygen on the surface to remove Si and remove P
A method for simultaneously performing the processing has been proposed, which aims at improving the P removal efficiency and reducing the attained P concentration.

[0003]

However, according to the method described in Japanese Patent Application Laid-Open No. 62-109910, the efficiency of de-Si and de-P removal of hot metal at the initial stage can be increased, but from the beginning to the end of the de-P process. Is performed under the same processing conditions, and the equilibrium mass transfer of phosphorus to slag or the like is not taken into account. As a result, the ultimate P concentration increases. In order to reduce the ultimate P concentration, the amount of quicklime, iron oxide, mill scale, oxygen, etc. used in the de-Si treatment and the de-P treatment increases, and the treatment cost increases. Furthermore, the amount of slag generated during the removal of Si and P is increased by using fresh quick lime, iron oxide, etc., and by increasing the amount of flux to be blown. Expensive. Further, in the method described in JP-A-6-287616, it is necessary to always use fresh quick lime, iron oxide and the like, and to use expensive raw materials such as CaF ₂ and Na ₂ O _3, and the amount of generated slag is required. Increase. In addition, since the generated slag contains a strong alkali component, fluorine, and the like, the generated slag is subject to environmental restrictions when discarded. Further, similarly to the method described in Japanese Patent Application Laid-Open No. 62-109910, from the initial stage to the final stage of the de-P treatment, the same treatment conditions are used to take into account the equilibrium mass transfer of phosphorus to slag and the like. Therefore, the de-P efficiency in the latter stage of the de-P process decreases, the amount of flux used for the preliminary treatment of de-Si and de-P increases, and the amount of slag generated increases. However, there is a problem that a large cost is required.

The present invention has been made in view of the above circumstances, and uses a converter type vessel to reduce the amount of flux used for the preliminary treatment of de-Si and de-P and the amount of generated slag, and to remove S
It is an object of the present invention to provide a pretreatment method for hot metal with a small amount of slag generation using a converter type vessel capable of increasing the reaction efficiency of the de-P reaction and reducing the attained Si and attained P concentrations.

[0005]

According to the present invention, there is provided a method for pre-treating molten iron having a small amount of slag using a converter type container according to the present invention. In the pretreatment method of hot metal with a small amount of slag to be treated, the slag generated in the previous pretreatment of hot metal
0-60% by weight is left in the converter type container,
A new hot metal is charged into the converter type vessel, and the hot metal is blown and subjected to a de-Si treatment and a de-P treatment. The flux is added to the hot metal during the de-Si treatment and the de-P treatment. Further, the above-mentioned Si removal processing and P removal processing are continuously performed. By this method, a part of the slag generated in the previous hot metal pretreatment in a region where the Si and P concentrations of the hot metal are high, which is a region of the oxygen supply law, is used for the pretreatment of newly charged hot metal, and By blowing acid, Si and P in the new hot metal can be oxidized and absorbed in the slag, and further, slagging of the flux added later can be promoted. Further, when the concentration of Si and P in the new hot metal charged in the converter type vessel becomes low, flux is added, and SiO ₂ or P ₂ O _{5 of} slag generated by slagging the flux at an early stage is added. Can be enhanced to promote the de-P reaction as well as the de-Si reaction, and to reduce the ultimate P concentration. If less than 40% by weight of the amount of slag generated in the previous hot metal pretreatment remains, the amount of slag becomes too small and SiO ₂ or P ₂ O ₅
The slag absorption capacity is reduced, the flux added later increases, and the pretreatment cost increases. On the other hand, 60% by weight
If the residual slag exceeds a certain value, the amount of slag that has absorbed SiO ₂ or P ₂ O ₅ increases to some extent, so that new flux is diluted into slag that has absorbed SiO ₂ or P ₂ O ₅ ,
The overall de-Si and de-P efficiencies are reduced. Furthermore, in order to lower the ultimate P concentration, it is necessary to increase the amount of the flux used, and the amount of generated slag increases, and the slag processing cost increases.

Here, in the pretreatment method for hot metal with a small amount of slag generated using the converter type container according to the present invention, the Si concentration of the new hot metal charged into the converter type container is 0.1 to 0.1. It is preferably 0.6% by weight. This makes it possible to oxidize Si in the new hot metal to generate SiO ₂ , absorb it into the slag, suppress the decrease in slag basicity, and promote the P removal reaction. If the Si concentration of the new hot metal is less than 0.1% by weight, the basicity of the generated slag increases, and the generated slag becomes poor in slag and the P removal reaction decreases. On the other hand, if the Si concentration exceeds 0.6% by weight, the basicity of the generated slag becomes too low, so that the absorption of P ₂ O _{5 in} the latter stage becomes poor, and the ultimate P concentration becomes high.

Further, in the method for pretreating hot metal with a small amount of slag generated using the converter type container according to the present invention, CaO is used as the flux, and the addition of the CaO is performed for 50 hours of the total elapsed time of the blowing acid. It is good to do it at the time of ~ 70%. This makes it possible to improve the slagging of the added flux, suppress the decrease in the FeO concentration in the slag, and stably increase the absorption capacity of the generated slag for SiO ₂ and P ₂ O ₅ . De-Si and De-P reactions can be promoted. If the time when the flux is added is less than 50% of the total elapsed time of the blowing acid, the amount of slag generated at the beginning of the blowing acid (when the flux is added) increases, and the FeO concentration in the slag decreases. And the efficiency of removing P decreases. On the other hand, if the time of addition of the flux exceeds 70% of the total elapsed time of the blowing acid, flux slagging during the flux pretreatment becomes poor, the P removal efficiency decreases, and the ultimate P concentration increases.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an overall view of an upper-bottom blow converter applied to a pretreatment method for hot metal with a small amount of slag using a converter type container according to one embodiment of the present invention. Figure 1
As shown in the above, an upper and bottom blown converter 10 which is an example of a converter type container used in a pretreatment method of hot metal with a small amount of slag using the converter type container according to one embodiment of the present invention,
A bottom blow nozzle 12 is provided at the bottom of the furnace body 11 and has an upper blow lance 13 inserted into the furnace body 11 from above.
A storage hopper 14 for storing quicklime (CaO) 15 which is an example of a flux for (silicon removal) and P removal (phosphorus removal), and a quicklime 15 cut out of the storage hopper 14 into a furnace 1
A chute 18 to be added to a slag 17 formed on the top of the hot metal 16 in the furnace 1 and a tapping port 19 provided on a side of the furnace body 11
It has.

Next, a method for pre-treating hot metal with a small amount of slag using the converter type container according to one embodiment of the present invention will be described using the above-described upper and lower blown converter 10.
First, the top and bottom blown converter 10 is set to a Si (silicon) concentration of 0.1.
0.6% by weight, P (phosphorus) concentration is 0.090 to 0.13
0% by weight of hot metal that has not been de-Si- or P-depleted
70 tons were charged, quicklime 15 was cut out from the storage hopper 14, added to the furnace body 11 via the chute 18, the upper blowing lance 13 was lowered, and inserted into the furnace body 11 to perform blowing acid, SiO ₂ and P generated by oxidizing Si and P
₂ O ₅ is absorbed into the slag, and de-Si and de-P treatments, which are preliminary treatments of the hot metal, are performed to reduce the Si concentration in the hot metal to 0.0%.
By adjusting the concentration of P to 1% by weight and the ultimate P concentration to 0.010% by weight, 5 tons of slag was generated after the pretreatment. The hot metal that has been subjected to the pre-treatment is tapped from the tap hole 19 to another container (not shown), and the slag generated in the pre-treatment is 40 to
60% by weight was left in the furnace body 11 of the top and bottom blown converter 10.

In the present embodiment, the above-described hot metal, that is, 40 to 60% by weight of the slag generated in the pretreatment of the previous hot metal (pre-charged hot metal) remains in the furnace In the furnace body 11 of the blow-down converter 10, the Si (silicon) concentration is 0.1 to 0.6% by weight, and the P (phosphorus) concentration is 0.1%.
170 tons of 090 to 0.130% by weight of fresh hot metal 16 (not subjected to de-Si and de-P treatment) is charged. Then, the upper blowing lance 13 is lowered, and the tip thereof is
The hot metal 16 in 1 was inserted at a position 1800 mm above the surface of the hot metal 16 to perform blowing acid (blowing of gaseous oxygen). Further, the pre-treatment of removing Si and P from the new hot metal 16 was performed while blowing a stirring gas such as argon gas and nitrogen gas for stirring the hot metal from the bottom blowing nozzle 12. In the treatment in the first half of the removal of Si and removal of P, molten iron 1
Most of the Si in 6 is oxidized to SiO ₂ and absorbed in the slag 17, completing the de-Si reaction. At this time,
As the de-Si reaction proceeds, P in the hot metal 16 is also oxidized to P ₂ O ₅ by the blown O and the slag 1
7, and a de-P reaction is performed. However, when the total time of the blowing acid at the time of the pretreatment is close to 50% of the total elapsed time of the blowing acid (the time from the start of the blowing acid to the end of the blowing acid), the slag 1
7, the ability to absorb P ₂ O ₅ decreases, and in the de-P reaction, P is less likely to be absorbed by the slag 17, that is, it enters the region of the P supply rule, so the de-P efficiency starts to decrease. Therefore, during the de-Si treatment and the de-P treatment, that is, 50 to 50 hours of the total elapsed time of the blowing acid
70% of the time, that is, within that time, quicklime 15
Is cut out from the storage hopper 14 and added to the hot metal 16 in the furnace body 11 via the chute 18, and further, the Si removal processing and the P removal processing are continuously performed.

If the quicklime 15 is added in a lump at the beginning of the removal of Si and the removal of P, the concentration of FeO in the slag does not increase.
In order to reduce the eO concentration or to cause poor slag slagging,
It is necessary to add evenly divided portions, or to add continuously little by little. The added quicklime 15 is easily mixed into the molten slag 17 and is a solid quicklime 15
And slag 17, which is a molten material, quickly dissolves, and the slag 17 can have an increased ability to absorb P ₂ O ₅ . As a result, even in the region of the P supply rule in which the de-P reaction hardly progresses, the oxidation of P and the P ₂ generated by this oxidation occur.
It is possible to promote the de-P reaction due to the absorption of O _{5 into} the slag 17, and this de-P reaction is achieved when the ultimate P concentration is 0.02
The process is performed until the content becomes 0.03% by weight. In addition, this escape S
i. Since the P removal process reuses 40 to 60% by weight of the slag generated during the pretreatment of the pre-charged hot metal, the amount of waste slag generated in the pretreatment of the hot metal is reduced. It is possible to reduce the amount of quicklime used, the cost of treating waste slag, and the like. Moreover, slag 1
Since 7 does not contain a strong alkali component such as Na or fluorine or a specific component, it is possible to eliminate environmental restrictions at the time of disposal. As described above, 40 to 60% by weight of the slag after the previous hot metal pretreatment is always used for the top and bottom blown converter 1
0, and new hot metal 16 is left in the furnace body 11.
After the removal of Si and P by blowing acid, preliminary treatment of adding CaO during the removal of Si and the removal of P is repeatedly performed. The hot metal 16 that has been subjected to the Si-removing process and the P-removing process is tapped from a tap hole 19, and charged into a decarburization refining furnace, such as an upper-blowing converter, an upper-bottom-blowing converter, or an electric furnace. Decarburization smelting by blowing acid is performed, thereby producing molten steel.

[0012]

Next, a description will be given of an embodiment of a method for pretreating hot metal with a small amount of slag generation using a converter type container according to the present invention. First, the silicon (Si) concentration is 0.3% by weight,
150 tons of pre-charged hot metal having a phosphorus concentration of 0.100% by weight is charged into the top and bottom blown converter 10, and CaO addition and blowing acid are performed to remove Si and P, and A part of the slag generated in the pre-charging pretreatment, the residual amount of the slag, the new hot metal having a phosphorus concentration of 0.100% by weight, ie, the silicon (Si) concentration of the hot metal of the next charge, Preliminary treatment for removal of Si and removal of P was performed by changing the charging timing of CaO on the way. Furnace body 1
1 was charged with 150 tons of new hot metal. Then, the ultimate P concentration (attained P weight%) after the pretreatment of the hot metal of the next charge and the generated slag amount index when the slag generation amount of the conventional pretreatment performed by adding quicklime and iron oxide is set to index 1 , And the overall evaluation were investigated. Table 1 shows the results.

Examples 1 and 2 used 50% by weight and 43% by weight of the residual slag of the pre-charge, respectively.
The case where the Si concentration at the time of charging the hot metal was 0.35% by weight and 0.42% by weight, and the addition timing of additional CaO was 55% and 63% of the total elapsed time of the blowing acid, respectively, was the ultimate P concentration. 0.013% by weight and 0.011% by weight, and the generated slag amount index could be 0.45 and 0.51, and a good (）) result was obtained as the overall evaluation. Example 3 is the case where the lower limit of the residual slag of the previous charge is 40% by weight, and Example 4 is the case where the upper limit of the residual slag of the previous charge is 60% by weight. 012% by weight, 0.015% by weight, the generated slag amount index is 0.5
4, 0.41 was obtained, and a good (）) result was obtained as the overall evaluation. In the fifth embodiment, the Si concentration of the next charge is set to 0.1.
0% by weight, Example 6 is the case where the Si concentration is 0.60% by weight, the ultimate P concentration is 0.012% by weight, 0.014% by weight, the generated slag amount index is 0.47,
0.48, and a good (○) result was obtained as the overall evaluation. Example 7 is the case where the additional CaO injection timing is set to the lower limit of 50%, and Example 8 is the case where the additional CaO input timing is set to the upper limit of 70%. 014% by weight, the generated slag amount index was 0.51 and 0.46, and a good (○) result was obtained as the overall evaluation.

[0014]

[Table 1]

On the other hand, in Comparative Example 1, the amount of residual slag used in the pre-charge was reduced to 33% by weight.
The amount of slag necessary for performing sufficient de-P is insufficient, and the ultimate P concentration at the end of the pretreatment becomes as high as 0.034% by weight, and the load in the decarburization refining process increases, resulting in poor overall evaluation. (×) The result was obtained. Comparative Example 2 is a case where the used amount of the residual slag slag of the previous charge was increased to 67% by weight, and the removal of P could be sufficiently performed, but the generated slag amount index was 0.1%.
82, which leads to an increase in waste disposal costs, etc.
The result was somewhat bad (△) as the overall evaluation. Comparative Example 3
Is the case where the Si concentration of the next charge is reduced to 0.05% by weight, the basicity of the slag at the time of the pretreatment increases,
The slag was poorly slagged, the de-P efficiency decreased, the ultimate P concentration increased to 0.037, the load in the decarburization refining process increased, and the overall evaluation was poor (x). Comparative Example 4
Is the case where the Si concentration of the next charge was increased to 0.67% by weight, the amount of slag generated increased due to the formation of SiO ₂ , and the generated slag amount index was slightly worse at 0.85. The de-P efficiency decreases due to the decrease in slag basicity,
The ultimate P concentration was as high as 0.032% by weight, and the result was poor (x) as the overall evaluation. Comparative Example 5 has additional CaO
Is set to 36%, which means that the charging time is too early, and the amount of slag in the initial stage of the start of the pretreatment increases, and with the increase in the amount of slag, the amount of Fe in the slag increases.
The O concentration decreased, the P removal efficiency throughout the entire pretreatment decreased, and the ultimate P concentration increased to 0.035% by weight, resulting in a poor (X) result as an overall evaluation. Comparative Example 6 is a case in which the additional CaO charging timing was 78%, and the charging timing was too late, resulting in poor slag slagging at the final stage of the pretreatment, resulting in a decrease in the P removal efficiency throughout the entire pretreatment. As a result, the ultimate P concentration was as high as 0.039% by weight, and the overall evaluation was poor (x). In the conventional method, the inside of the furnace 11
This is the case where the hot metal charged into the furnace is always subjected to de-Si and de-P treatment of hot metal by adding fresh quick lime and iron oxide to perform blowing acid, and the amount of quick lime and iron oxide added during the entire pretreatment Increase, the generated slag amount index becomes high as 1.0,
Since the cost of disposal was increased, the overall evaluation was bad (x).

The embodiments of the present invention have been described above.
The present invention is not limited to the above-described embodiment, and all changes in conditions that do not depart from the gist are within the scope of the present invention. For example, in the present embodiment, the flux is Ca
Although the case where O is used has been described, a flux generally used for de-P, such as dolomite and limestone, can be used in addition to CaO. Furthermore, Si in hot metal,
When P is oxidized, sludge,
Solid oxygen agents such as dust dust, iron ore, and scale can be used in combination with the blowing acid.

[0017]

According to the pretreatment method for hot metal with a small amount of slag generated using the converter type container according to claims 1 to 3,
40-60% by weight of the slag generated in the previous hot metal pretreatment is left in the converter type vessel, new hot metal is charged into the converter type vessel, and the molten iron is blown off to remove Si. In the course of the de-Si treatment and the de-P treatment, a flux is added to the hot metal, and the de-Si treatment and the de-P treatment are continuously performed. Can be saved, the efficiency of de-Si and de-P can be increased, the attained Si and P concentrations can be reduced, and the disposal cost of waste slag can be reduced.

According to a second aspect of the present invention, there is provided a method for pretreating hot metal with a small amount of slag using a converter type container, wherein the Si concentration of new hot metal charged into the converter type container is 0.1 to 0.1.
Since the content is set to 6% by weight, it is possible to suppress an excessive increase in the amount of slag and a decrease in basicity of the slag, stably increase the de-Si and de-P efficiencies, and lower the attained Si and attained P concentrations. In addition, the load of the decarburization refining in the post process can be reduced.

According to a third aspect of the present invention, there is provided a method for pre-treating hot metal with a small amount of slag using a converter type container, wherein CaO is used as a flux, and the addition of CaO is 50 to 70% of the total elapsed time of the blowing acid. Since the slag is formed at a suitable time, it is possible to improve the slag slaging, improve the efficiency of de-Si and de-P with a small amount of slag, suppress harmful components such as alkali components of the generated slag, and reuse the slag. It can be carried out.

[Brief description of the drawings]

FIG. 1 is an overall view of an upper-bottom blow converter applied to a pretreatment method for hot metal with a small amount of slag generation using a converter type container according to one embodiment of the present invention.

[Explanation of symbols]

10: top and bottom blown converter (converter type vessel), 11: furnace body, 1
2: bottom blowing nozzle, 13: top blowing lance, 14: storage hopper, 15: quick lime (flux), 16: hot metal, 1
7: slag, 18: chute, 19: tapping outlet

Claims (3)

[Claims] In a pretreatment method of hot metal with a small amount of slag generated by performing a de-Si treatment and a de-P treatment using a converter-type container, the slag generated in the previous pre-treatment of the hot metal is reduced.
0-60% by weight is left in the converter type container,
A new hot metal is charged into the converter type vessel, and the hot metal is blown and subjected to a de-Si treatment and a de-P treatment. The flux is added to the hot metal during the de-Si treatment and the de-P treatment. Further, a pretreatment method for hot metal with a small amount of slag generation using a converter type vessel, wherein the de-Si treatment and the P removal treatment are continuously performed. 2. The method for pretreating hot metal with a small amount of slag generated using the converter type container according to claim 1, wherein the Si concentration of the new hot metal charged into the converter type container is 0.1%.
A pretreatment method for hot metal with a small amount of slag generation using a converter type vessel, characterized in that the content is 1 to 0.6% by weight. 3. A pretreatment method for hot metal with a small amount of slag generation using the converter type container according to claim 1 or 2,
Using CaO as the flux, wherein the addition of the CaO is performed at a time corresponding to 50 to 70% of the total elapsed time of the blowing acid; Method.