JP5467794B2 - Dephosphorization method for hot metal with low dust generation - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a hot metal dephosphorization method that performs dephosphorization of hot metal by continuously supplying a dephosphorizing agent and oxygen to the hot metal in a kneading vehicle.

Conventionally, various techniques have been disclosed in which hot metal discharged from a blast furnace is charged into a kneading car (topy car) and the hot metal is dephosphorized by the kneading car. In such a dephosphorization process, for example, there is a technique disclosed in Patent Document 1 that prevents the process from being interrupted by slag forming.
In Patent Document 1, iron oxide and a refining flux are blown into a hot metal held in a transfer container with a carrier gas through an immersion lance, and oxygen gas is supplied through a lance separately provided above the bath surface of the hot metal. When the bath surface is sprayed, the hot metal desiliconization, and the dephosphorization process are sequentially performed, the flow rate of the oxygen gas to be blown is changed according to the change in the composition of the hot metal during the desiliconization and dephosphorization processes.

As shown in Patent Document 1, although not intended to suppress slag forming, Patent Document 2 and Patent Document 3 disclose hot metal dephosphorization processing in a kneading vehicle.
In Patent Document 2, when degassing hot metal using a converter slag as a dephosphorization component in a container in which the amount of hot metal put into the container is 50% or more and less than 100% of the container volume, A massive converter slag is used as the furnace slag, and this massive converter slag is added from above the hot metal.

  In Patent Document 3, when the molten iron dephosphorization process is performed in a kneading vehicle using the converter slag as a dephosphorization component, the oxygen-containing gas is supplied from the upper surface of the molten metal to the molten iron over 80% of the total dephosphorization time. The secondary board is sprayed to increase the temperature of the free board.

JP 2004-149876 A JP 2002-285219 A JP 2001-329309 A

  Patent Document 1 discloses that the flow rate of oxygen gas to be blown up is changed in accordance with changes in the hot metal component. However, changing the flow rate of oxygen gas is caused by the formation of slag from the chaotic vehicle. It is intended to prevent the chaotic vehicle tracks from being buried by overflowing and overflowing slag. That is, Patent Document 1 is for suppressing forming that occurs during the dephosphorization process, and is performed to reduce dust generation during the dephosphorization process. Even if it does, it is the actual condition that the dust generation which generate | occur | produces in the case of a dephosphorization process cannot be suppressed.

In addition, Patent Document 2 and Patent Document 3 disclose that hot metal dephosphorization processing is performed in a kneading vehicle, but even if these techniques are used, dust generation that occurs during dephosphorization processing is suppressed. The fact is that you can't.
Therefore, in view of the above problems, the present invention can suppress dust generation when performing dephosphorization processing of hot metal by continuously supplying a dephosphorizing agent and oxygen to the hot metal in a kneading vehicle. It aims at providing the dephosphorization method of hot metal with little dust.

In order to achieve the above object, the present invention has taken the following measures.
That is, the technical means for solving the problems in the present invention is to remove hot metal by continuously supplying CaO or a solid dephosphorizing agent containing CaO and O and gaseous oxygen to the hot metal in the kneading vehicle. In the method of performing the treatment, at the start of the hot metal dephosphorization treatment, the total oxygen supply rate of the total of O ₂ contained in the solid dephosphorization agent and O ₂ of the gaseous oxygen is set to 0 to 0.07 Nm ³ / t. / min and to keep, at less than 0.15 mass% to 0.20 mass% [Si] in the molten iron, raising the total oxygen feed rate in the range of 0.10~0.23Nm ³ / t / min, When [Si] in the hot metal is 0.10% by mass or more and less than 0.13% by mass, the total oxygen supply rate is further increased to a range of 0.25 to 0.35 Nm ³ / t / min to generate dust. It is in the point which suppresses.

  ADVANTAGE OF THE INVENTION According to this invention, when performing a dephosphorization process of a hot metal by supplying a dephosphorizing agent and oxygen continuously to the hot metal in a kneading vehicle, dust generation can be suppressed.

It is a figure which shows the dephosphorization process of the hot metal by a kneading vehicle. It is a figure which shows the range which changes a total oxygen supply rate in each step. 1 is a diagram illustrating Example 1. FIG. FIG. 10 is a diagram illustrating Example 11. 14 is a diagram illustrating a comparative example 14. FIG. 16 is a diagram illustrating a comparative example 15. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a hot metal dephosphorization process using a kneading wheel.
As shown in FIG. 1, in order to dephosphorize the molten iron 2 with the kneading vehicle 1, first, the molten iron 2 discharged from the blast furnace is charged into the container 3 of the kneading vehicle 1 and removed with the kneading vehicle 1. The chaotic vehicle is moved to the dephosphorization station for the phosphorus treatment. In the dephosphorization station, a blowing lance 5 for blowing gaseous oxygen to the molten iron 2 is inserted into the opening 4 in the container 3 of the kneading wheel 1 and a solid dephosphorizing agent or the like is blown into the molten iron 2. The blowing lance 6 is inserted. Further, at the dephosphorization station, the dust collecting hood 7 is arranged so as to cover the upper part of the opening 4 of the chaotic vehicle 1.

In such a state, gaseous oxygen is blown toward the hot metal 2 by the spray lance 5 and a solid dephosphorizing agent is blown by the blow lance 6 toward the hot metal 2 so that the hot metal 2 is dephosphorized. Done. At this time, the exhaust gas containing the dust generated by the dephosphorization process is sucked by the dust collection hood 7 and sent to the dust collector.
Hereinafter, the dephosphorization method of the hot metal 2 of the present invention will be described in detail.
The solid dephosphorizing agent blown into the hot metal 2 contains CaO or CaO and O, and specifically, is quick lime blown as a CaO source and iron oxide blown as O (oxygen source). That is, in the dephosphorization treatment of the hot metal 2, both quick lime and iron oxide are supplied to the hot metal 2 as solid dephosphorizing agents, or only quick lime excluding the iron oxide source is supplied.

As described above, the dephosphorization method for the hot metal 2 of the present invention is performed by the kneading vehicle 1, and the hot metal 2 is continuously supplied with a solid dephosphorizing agent and a gaseous oxygen source in the dephosphorization process. It is intended for those that perform the dephosphorization process of 2. That is, the present invention is based on the premise that the molten oxygen 2 is dephosphorized by continuously blowing gaseous oxygen with the blowing lance 5 and continuously blowing the solid dephosphorizing agent with the blowing lance 6. Has been.
Now, in the initial stage of the dephosphorization treatment of the hot metal 2, when [Si] in the hot metal 2 is high, CaO (quick lime) reacts with Si in the hot metal 2 to generate SiO ₂ preferentially. Become. At this time, a portion having a high SiO ₂ concentration (for example, a CaO · SiO ₂ phase) is generated in the upper portion (top slag) of the slag, and thereby the viscosity of the slag becomes very high.

Thus, when the viscosity of the slag is high, the CO gas generated during the dephosphorization process is difficult to escape upward from the inside of the slag. Dust generation may increase due to bubble breakage.
Therefore, in the hot metal 2 dephosphorization method, as shown in FIG. 2, when the dephosphorization process is started, when [Si] in the hot metal 2 is high, that is, when the dephosphorization process is started. (first time of supplying gaseous oxygen and dephosphorization agent into molten pig iron 2), the total oxygen feed rate which is the sum of the O ₂ in the O ₂ and gaseous oxygen contained in a solid dephosphorization agent, 0～0.07Nm ³ The generation of CO gas is suppressed by keeping constant in the range of / t / min and lowering the degree of oxygen supply supplied to the hot metal 2. For convenience of explanation, the stage in which the dephosphorization process is started and the total oxygen supply rate is made constant in the above-described range (0 to 0.07 Nm ³ / t / min) may be referred to as the first stage.

Here, O ₂ contained in the solid dephosphorizing agent is O ₂ (oxygen) contributing to the dephosphorylation reaction, that is, dissolved oxygen as shown by 2P + 5O (dissolved oxygen) + 3O ²⁻ → 2PO ₄ ^3−. Specifically, O ₂ (oxygen) contained in iron oxide (FeO or Fe ₂ O ₃ ) in the solid dephosphorizing agent is shown. Since CaO does not contribute to the reaction as an oxygen component in the dephosphorization treatment, oxygen in the CaO is not included as is well known. O _{2 of} gaseous oxygen is oxygen blown from the spray lance 5 toward the hot metal 2 separately from iron oxide.
That is, the solid O ₂ and the gaseous oxygen O ₂ and the total oxygen feed rate which is the sum of that contained in the dephosphorization agent, a value obtained by converting the oxygen oxidation in the iron supplied to the hot metal 2 in the oxygen supply rate, gaseous oxygen And the value obtained by converting the oxygen supply rate of the above, and can be obtained by, for example, the equation (1).

In dephosphorization process, desiliconization proceeds, gradually reduced [Si] in the molten iron 2, is a less than 0.20 mass% to 0.15 mass%, with the rate of formation of SiO ₂ is gradually lowered Part of the slag changes, for example, from the CaO · SiO ₂ phase to the 3CaO · 2SiO ₂ phase (the 3CaO · 2SiO ₂ phase increases), so that the SiO ₂ concentration of the top slag is at the start of the dephosphorization process. Lower than (initial stage). Therefore, when [Si] in the hot metal 2 is 0.15% by mass or more and less than 0.20% by mass, the CO gas easily escapes from the slag as compared with the initial stage of the dephosphorization treatment. Even if it is slightly raised from the stage, it is possible to suppress dust generation due to bubble breakage of CO gas.

Therefore, as shown in FIG. 2, in the dephosphorization process of hot metal 2, in the molten iron 2 [Si] is less than 0.15 wt% 0.20 wt%, 0.10 nm the total oxygen feed rate ³ / The temperature is increased to t / min or more and is shifted from the first stage to the second stage.
Here, as described above, a the [Si] is less than 0.20 mass% to 0.15 mass% in the hot metal 2, is CO gas tends escape from the slag than in the early stages of dephosphorization treatment However, when the total oxygen supply rate is increased by exceeding 0.23 Nm ³ / t / min when the total oxygen supply rate is increased, the SiO 2 concentration slightly remaining in the upper portion of the slag (top slag) Since there is a part where the viscosity of the slag is high due to the influence of the high part, this may cause the bubble breakage of the CO gas. For this reason, the upper limit value of the total oxygen supply rate when shifting from the first stage to the second stage is 0.23 Nm ³ / t / min.

That is, in the present invention, in a first stage, in the molten iron 2 [Si] is less than 0.15 mass% to 0.20 mass%, the total oxygen feed rate 0.10~0.23Nm ³ / t / min In the second stage, the increased total oxygen supply rate is kept constant. In this way, by switching the total oxygen supply rate from the first stage to the second stage, the reaction by the dephosphorization process is promoted while suppressing the generation of dust due to the bubble breakage of the CO gas.
In addition, after [Si] in the hot metal 2 becomes less than 0.15 mass%, the total oxygen supply rate is increased from the first stage to the second stage (the total oxygen supply speed is 0.10 to 0.23 Nm). ³ / t / min), however, with this amount of increase, it is considered that the processing time of the dephosphorization process becomes too long and it becomes difficult to use industrially.

Now, paying attention to the state of the slag when the [Si] in the hot metal 2 becomes less than 0.15% by mass, in such a case, the [Si] in the hot metal 2 is 0.15% by mass or more and 0.0. than when less than 20 wt%, with the rate of formation of SiO ₂ is further lowered, it is considered that is even lower concentration of SiO ₂ in the top slag. That is, when [Si] in the hot metal 2 is less than 0.15 mass, compared to when [Si] in the hot metal 2 is 0.15 mass% or more, a part of the slag in the top slag is, for example, Since it changes from a CaO.SiO ₂ phase to a CaO.SiO ₂ phase (CaO.SiO ₂ phase increases), a highly viscous portion hardly occurs, the viscosity of slag is relatively low, and CO gas is slag. It can be said that it is in a state where it is more easily removed from.

Therefore, in the present invention, when the molten iron 2 [Si] is less than 0.15 wt%, in particular, in less than 0.13 wt% [Si] is more than 0.10 mass%, than the second step described above However, the total oxygen supply rate is further increased to shift to the third stage in which the total oxygen supply rate is increased.
Specifically, in the second stage, the molten iron 2 [Si] is the less than 0.10 mass% to 0.13 mass%, of the total oxygen feed rate 0.25~0.35Nm ³ / t / min The range is switched to the third stage, and in the third stage, the increased total oxygen supply rate is kept constant. Thus, by switching the total oxygen supply rate from the second stage to the third stage, the reaction due to the dephosphorization process is further promoted while the dust generation due to the bubble breakage of the CO gas is suppressed.

If the total oxygen supply rate exceeds 0.35 Nm ³ / t / min during the transition from the second stage to the third stage, the generation rate of CO gas will increase too much, resulting in generation of dust. For this reason, when switching from the second stage to the third stage, the upper limit value of the total oxygen supply rate is set to 0.35 Nm ³ / t / min.
Here, it is considered that the total oxygen supply rate is increased from the second stage to the third stage after [Si] in the hot metal 2 becomes less than 0.10% by mass. When the total oxygen supply rate is increased after less than 10% by mass, the timing for increasing the total oxygen supply rate is too late. As a result, it is considered that the processing time of the dephosphorization process becomes too long and it becomes difficult to use industrially. Therefore, even if switching to the increase in the total oxygen supply rate is slow, [Si] in the hot metal 2 is 0.10. It is necessary to carry out when the content is at least mass%.

As described above, according to the present invention, at the start of the dephosphorization treatment of the hot metal 2, the total oxygen supply rate is set to 0 to 0.07 Nm ³ / t / min, and then [Si] in the hot metal 2 is 0.15. in less mass% to 0.20 mass%, the total oxygen feed rate was Noboru Ue the range of 0.10~0.23Nm ³ / t / min, further, the molten iron 2 [Si] is 0.10 wt% in more than 0.13 wt%, and the total oxygen feed rate was Noboru Ue the range of 0.25~0.35Nm ³ / t / min. In other words, according to the present invention, according to [Si] in the hot metal 2, the total oxygen supply rate of oxygen supplied to the hot metal 2 is divided into three stages (first stage to third stage), and the first stage. Thus, by performing a switching process for gradually increasing the total oxygen supply rate, the processing efficiency in the dephosphorization process is improved while maintaining a small amount of dust generation.

  In addition, the calculation of [Si] of the hot metal 2 described above is performed according to the ordinary method of those skilled in the art, and can be obtained by, for example, the equation (2).

  In Formula (2), the pre-treatment Si is a value obtained by analyzing [Si] in the hot metal 2 before performing the dephosphorization treatment, and the pre-change oxygen supply rate Si increases the total oxygen supply rate. This shows the total oxygen supply rate in the previous stage, and was obtained by calculation. For example, when shifting from the first stage to the second stage, the molten iron Si uses the Si reduction width at the time of supplying Si-oxygen before processing (the amount of Si reduction when oxygen is supplied in the first stage). . In the transition from the second stage to the third stage, the molten iron Si is not changed from the total oxygen supply rate Si (Si at the end of the first stage) to the Si reduction width at the time of oxygen supply (oxygen is added in the second stage). Si reduction when supplied) is used. Note that the supply time of the formula (2) is the time during which oxygen is supplied in each stage (in other words, the time during which a solid dephosphorizing agent containing O and / or gaseous oxygen is supplied). The desiliconization oxygen efficiency was set to 0.7 with reference to FIG. 6 described in Iron and Steel, Vol.

  Table 1 summarizes the operating conditions, and Table 2 summarizes the solid dephosphorizing agents shown in Table 1. Table 3 shows an example in which dephosphorization treatment was performed by the dephosphorization method for hot metal 2 of the present invention and a comparative example in which dephosphorization treatment was performed by a method different from the dephosphorization method for hot metal 2 of the present invention. It is a summary.

  As shown in Table 1, there are three types of solid dephosphorizing agents: dephosphorizing agent A, dephosphorizing agent B, and dephosphorizing agent C. The supply rates of the supplying agents shown in Table 1 are dephosphorizing agent A and dephosphorizing agent. It is a value when supplying agent B, dephosphorizing agent C and gaseous oxygen to hot metal 2. Various components of the dephosphorizing agent A, dephosphorizing agent B, and dephosphorizing agent C are shown in Table 2.

As shown in Table 2, the amount of O ₂ contained in each dephosphorizing agent A (the amount of O ₂ contained) was determined by the formula (3).

  Tables 3 and 4 show that the hot metal 2 was dephosphorized by the method of the present invention based on the operating conditions shown in Table 1 and the method of the hot metal 2 was different from the method of the present invention. The comparative example which performed the dephosphorization process is put together.

As shown in Tables 3 and 4, in Examples and Comparative Examples, dust that cannot be sucked by the dust collection hood 7 at each stage was visually recognized (dust generation from the dust collection hood 7 The dust generation was “present”, and the case where no dust was visually observed was determined as “no”. The dust collection hood 7 is a general one as disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-149876, and the size of the integrated hood 7 (the size covering the opening 4 and the size of the opening 8). The arrangement is also standard.
The Si concentration (calculated value) at the time of switching shown in the examples and the comparative examples is obtained from the Si reduction width during oxygen supply shown in Equation (2).

FIG. 3 illustrates the first embodiment. As shown in FIG. 3 and Table 3, in Example 1, first, in the first stage after the dephosphorization treatment of the hot metal 2 was started, the total oxygen supply rate was constant at 0.0497 Nm ³ / t / min. . When the [Si] in the hot metal 2 reaches 0.198% by mass, the total oxygen supply rate is increased to 0.219 Nm ³ / t / min (second stage). Furthermore, when the [Si] of the hot metal 2 reaches 0.112% by mass, the total oxygen supply rate is increased to 0.311 Nm ³ / t / min (third stage-1). There are two third stages. In the second third stage, the total oxygen supply rate is 0.257 Nm ³ / t / after the calculated [Si] of the molten iron 2 becomes 0 mass%. (Minute 3).

FIG. 4 illustrates the eleventh embodiment. As shown in FIG. 4 and Table 3, in Example 11, first, in the first stage after the dephosphorization treatment of the hot metal 2 was started, the total oxygen supply rate was made constant at 0.0571 Nm ³ / t / min. . When the [Si] of the hot metal 2 reaches 0.185% by mass, the total oxygen supply rate is increased to 0.182 Nm ³ / t / min (second stage). Furthermore, when the [Si] of the hot metal 2 reaches 0.129% by mass, the total oxygen supply rate is increased to 0.303 Nm ³ / t / min (third stage-1). In Example 11, as shown in Example 1, there are two third stages, but the second time in the third stage is the total amount after the calculation of [Si] in the molten iron 2 becomes 0 mass%. The oxygen supply rate is reduced to 0.182 Nm ³ / t / min (third stage-2).

Thus, even in the case of increasing the total oxygen supply rate stepwise in the dephosphorization treatment, [Si] in the hot metal 2 became 0 mass% as in the second stage of the third stage. After the time, there is no problem even if the total oxygen supply rate is lowered.
In other examples, the process was performed as shown in FIGS. 3 and 4 except for Example 5. In Example 5, in the second round of the third stage, the total oxygen supply rate was increased to 0.261 Nm ³ / t / min (third stage-2). As in Example 5, if [Si] of the hot metal 2 becomes 0 mass%, even if the total oxygen supply rate is increased, the upper limit is 0.35 Nm ³ / t / min or less, no problem. There is no.

As described above, as shown in Examples 1 to 13, at the start of the dephosphorization treatment of the hot metal 2, the total oxygen supply rate obtained by totaling O ₂ contained in the solid dephosphorization agent and O ₂ of the gaseous oxygen is 0~0.07Nm ³ / t / min and to keep, in the molten iron 2 [Si] is less than 0.15 mass% to 0.20 mass%, the total oxygen feed rate 0.10~0.23Nm ³ / t / min range is above the temperature of, the less than 0.10% by mass or more 0.13 wt% [Si] in the molten iron 2, further total oxygen feed rate 0.25~0.35Nm ³ / t / min if so as to Noboru Ue in the range of, without dusting occurs at any stage, it was possible to perform the dephosphorization process. In particular, in Example 1 to Example 13, the time from the first stage to the end of the third stage (total processing time) could be within 48 minutes, and no dust was generated.

FIG. 5 illustrates Comparative Example 14. As shown in FIG. 5 and Table 3, in Comparative Example 14, first, in the first stage after the dephosphorization treatment of the hot metal 2 was started, the total oxygen supply rate was constant at 0.0833 Nm ³ / t / min. . When the [Si] of the hot metal 2 reaches 0.215% by mass, the total oxygen supply rate is increased to 0.267 Nm ³ / t / min (second stage). Furthermore, when the [Si] of the hot metal 2 reaches 0.169% by mass, the total oxygen supply rate is increased to 0.392 Nm ³ / t / min (third stage-1). In Comparative Example 14, in the second round of the third stage, the total oxygen supply rate was reduced to 0.257 Nm ³ / t / min after [Si] in the calculated molten iron 2 became 0 mass%. (Third stage-2).

In Comparative Example 14, in the first stage where the treatment of the hot metal 2 was started, the total oxygen supply rate was as high as 0.0833 Nm ³ / t / min, and even when the [Si] in the hot metal 2 was high, the total oxygen supply was greatly increased. The speed is increased (second stage). Therefore, the total processing time is 32 minutes, which is very short compared to the example, but dust generation occurred in both the first stage and the second stage.
Moreover, as shown in Comparative Example 18, Comparative Example 23 and Comparative Example 24, when [Si] in the hot metal 2 is high as in Comparative Example 14, the total oxygen supply rate is significantly increased (second stage). ), Dust was generated.

FIG. 6 illustrates Comparative Example 15. As shown in FIG. 6 and Table 3, in Comparative Example 15, first, in the first stage after the dephosphorization treatment of the hot metal 2 was started, the total oxygen supply rate was constant at 0.12 Nm ³ / t / min. . When the [Si] in the hot metal 2 reaches 0.199% by mass, the total oxygen supply rate is lowered to 0.091 Nm ³ / t / min (second stage). Furthermore, when the [Si] of the hot metal 2 reaches 0.175% by mass, the total oxygen supply rate is increased to 0.194 Nm ³ / t / min (third stage-1).
Therefore, although the total oxygen supply rate in the first stage is large, the total oxygen supply rate in the second stage is very small, so the total processing time is as long as 56 minutes. Moreover, dust generation occurred because the total oxygen supply rate was too high in the first stage.

As shown in Comparative Example 14 to Comparative Example 26, when processing is performed so as to deviate from the scope of the present invention at each stage, when dust generation occurs at a stage out of conditions, or processing time May be longer.
Therefore, according to the present invention, in the dephosphorization process of the hot metal 2 by the kneading vehicle 1, it is possible to efficiently perform the dephosphorization process of the hot metal 2 while suppressing the generation of dust.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Chaotic wheel 2 Hot metal 3 Container 4 Opening part 5 Blowing lance 6 Blowing lance 7 Dust collection hood 8 Opening part

Claims (1)

In a method of performing dephosphorization treatment of hot metal by continuously supplying CaO or a solid dephosphorization agent containing CaO and O and gaseous oxygen to the hot metal in the kneading vehicle,
At the start of the dephosphorization process of hot metal, the total oxygen feed rate to the sum and O ₂ containing a O ₂ of the gaseous oxygen in the solid dephosphorization agent, leave the 0~0.07Nm 3 ^/ t / min,
In less than 0.15 wt% to 0.20 wt% [Si] in the molten iron, raising the total oxygen feed rate in the range of 0.10~0.23Nm ³ / t / min,
When [Si] in the hot metal is 0.10% by mass or more and less than 0.13% by mass, the total oxygen supply rate is further increased to a range of 0.25 to 0.35 Nm ³ / t / min to generate dust. A dephosphorization method for hot metal with less dust generation, characterized by suppressing slag.