JP2009287083A - Method for dephosphorizing molten pig iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which simultaneously prevents slag formation and slag deposition occurring when decreasing the phosphorus concentration P [wt.%] of a molten pig iron to 0.06% or less, which has had 0.09% or more of phosphorus concentration P [wt.%], by blowing a dephosphorizing agent together with a carrier gas into the molten pig iron. <P>SOLUTION: The dephosphorizing agent satisfies the composition comprising CaO: 14 to 18 wt.%, SiO<SB>2</SB>: 5 to 8 wt.%, t. Fe: 48 to 55 wt.%, O: 19 to 25 wt.%, CaO/O: 0.75 to 1.10, and C/S: 2.2 to 3.0. A unit consumption [kg/ton] of CaO, which is total lime unit consumption, shall be controlled to 20 or less. A blowing velocity V<SB>INJ</SB>[kg/min] of the dephosphorizing agent shall be controlled to 600 or less. A solid-gas ratio R<SB>INJ</SB>[kg/Nm<SP>3</SP>], which is the ratio of the dephosphorizing agent to the carrier gas, shall be controlled to 30 to 46. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hot metal dephosphorization method.

  As this kind of technology, Patent Document 1 discloses, as a hot metal pretreatment method, hot metal is received in a topped car, a desulfurizing agent is introduced using nitrogen gas as a carrier gas, and then sintered ore and quicklime are used using an oxygen-containing gas as a carrier gas. It is described that de-P is performed by blowing de-P flux composed of Table 1 of Patent Document 1 illustrates several blending amounts of sintered ore and quicklime as materials for removing P flux. For example, the mixing ratio of quicklime is 19.5%, 220.9%, 20.8%, 21.5%, or the like.

  Patent Document 2 discloses a lime-based dephosphorizing agent used for hot metal blowing. This dephosphorizing agent is a mixture of a raw material pulverized in advance through a melting process and a powder raw material containing calcium oxide, and its composition is 35 to 55% CaO. The above-mentioned “crushed raw material” is one that has been melted and then solidified once, and converter slag has been introduced as an example. It is stated that if the amount of CaO in the dephosphorization agent is less than 35%, rephosphorization is likely to occur after the dephosphorization treatment. Moreover, since a part of the dephosphorizing agent is previously melted, it is described that the wettability of the dephosphorizing agent and the hot metal is good.

Japanese Patent No. 3797206 Patent No. 3503176

By the way, what is known as a slag foaming phenomenon is known when performing dephosphorization of hot metal in a kneading vehicle. For example, see "Iron and Steel" (Vol. 78, No. 2 (1982), p. 200-208). According to this document, as a general property of the above-mentioned foaming phenomenon (hereinafter also referred to as slag forming), the lower the basicity of slag, the lower the basic unit of lime, or the higher the acid feed rate, the higher the rate of CO gas. The generation speed is increased, and slag forming is likely to occur. On the other hand, torpedo car of the free board, in general, the hot metal 1tp per 0.13m about ³ (about 0.2m ³ at most) only can not be secured. Therefore, once slag forming starts, it cannot be avoided that the slag flows out of the chaotic vehicle. Therefore, the applicant of the present application has set the ratio of CaO as the dephosphorizing agent to be large (for example, to the extent disclosed in Patent Document 1 and Patent Document 2) in order to suppress the occurrence of the slag forming.

  However, another problem has arisen in the above operation. That is, if the hot metal is transferred from the kneading car to the converter after the dephosphorization process and the slag remaining in the kneading car is to be discharged, there is slag that cannot be removed by adhering to the inner wall of the kneading car. There was a tendency that the volume of the chaotic car itself gradually decreased because the car could not be discharged sufficiently.

  The present invention has been made in view of these points, and its main purpose is to blow a dephosphorizing agent together with a carrier gas into hot metal having a phosphorus concentration P [wt%] of 0.09% or more. An object of the present invention is to provide a technique for simultaneously preventing slag forming and slag adhesion when the phosphorus concentration P [wt%] of the hot metal is set to 0.06 or less. Another object of the present invention is to provide a technique for producing a dephosphorizing agent having excellent dephosphorization efficiency.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above, and the inventors of the present invention have determined that the composition of the dephosphorizing agent is unique in order to prevent slag forming and slag adhesion at the same time after extensive research. As a result, the following invention was completed. Next, means for solving the above problems and effects thereof will be described.

According to the aspect of the present invention, the dephosphorization of the hot metal is performed by the following method. That is, the dephosphorizing agent satisfies the following composition. The CaO basic unit [kg / ton] as the total lime basic unit is 20 or less. The dephosphorization agent blowing speed V _INJ [kg / min] is set to 600 or less. A solid-gas ratio R _INJ [kg / Nm ³ ], which is a ratio between the dephosphorizing agent and the carrier gas, is set to 30 to 46.
CaO [wt%]: 14-18
SiO ₂ [wt%]: 5~8
t. Fe [wt%]: 48 to 55
O [wt%]: 19 to 25
CaO / O: 0.75 to 1.10
C / S: 2.2 to 3.0

  According to the above method, slag forming and slag adhesion can be prevented simultaneously.

  Here, the reason why the dephosphorization method according to the present invention is intended only for the operation in which the phosphorus concentration P [wt%] of the molten iron after treatment is set to 0.06 or less will be briefly described. That is, if the phosphorus concentration P [wt%] of the hot metal is already 0.06 or less during the decarburization process in the subsequent converter, the various raw materials and the processing time required for the operation of brewing to casting are reduced. Because it can be reduced as.

  Going back, the above-mentioned Patent Document 1 and Patent Document 2 do not mention any slag adhesion.

  The above hot metal dephosphorization is further performed by the following method. That is, the dephosphorizing agent is produced by blending sintered ore and calcined lime. The dephosphorizing agent produced by the above method is easily melted in the hot metal, and thus has excellent dephosphorization efficiency.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, a predetermined amount of hot metal discharged from the blast furnace is received in a kneading car, and the hot metal is transported to a hot metal pretreatment facility using this kneading car. The phosphorus concentration P [wt%] of the hot metal is generally 0.09% or more.

  When the kneading vehicle arrives at the hot metal pretreatment facility, the dephosphorization treatment is performed on the molten iron by blowing a dephosphorizing agent together with a carrier gas to the molten metal accommodated in the kneading vehicle. Hereinafter, the dephosphorization process in the hot metal pretreatment facility will be described in detail.

<Dephosphorizing agent>
First, the above dephosphorizing agent will be described in detail. The above dephosphorizing agent has the following composition. However, the following “t.Fe” means total iron, and “C / S” means so-called basicity.
CaO [wt%]: 14-18
SiO ₂ [wt%]: 5~8
t. Fe [wt%]: 48 to 55
O [wt%]: 19 to 25
CaO / O: 0.75 to 1.10
C / S: 2.2 to 3.0

The above dephosphorizing agent is produced, for example, by appropriately blending sintered sinter and calcined lime. Sintered ore is an under-sieved sintered ore generated during the iron ore sintering process, and has a particle size of about 2 to 5 mm (average particle size: about 3 mm). A general composition of the sintered ore is described in, for example, Japanese Patent No. 3740894, and for example, has the following composition.
CaO [wt%]: 11
Al ₂ O ₃ [wt%]: 1
MgO [wt%]: 1
SiO ₂ [wt%]: 7
The rest: iron oxide

In order to promote the dephosphorization reaction, the dephosphorizing agent is preferably pulverized to have an average particle diameter φ _AVE of about 100 μm, for example.

  Furthermore, the CaO basic unit [kg / ton] as the total lime basic unit put into the chaotic vehicle is set to 20 or less. Here, “ton” refers to the weight of the hot metal.

<Blowing of dephosphorizing agent>
Next, the blowing of the dephosphorizing agent into the hot metal will be described in detail. Reference is now made to FIG. FIG. 1 is a schematic cross-sectional view of a kneading vehicle during a dephosphorization process.

  As shown in the figure, the dephosphorizing agent is blown into the hot metal together with the carrier gas by using a refractory blowing lance whose lower end is immersed in the hot metal in the kneading vehicle. In the present embodiment, the blowing lance is vertically inserted into the kneading vehicle through a slag discharge hole formed in the center of the kneading vehicle. The carrier gas may be any gas as long as it is inert to the hot metal, and examples thereof include nitrogen gas and argon gas. In this embodiment, nitrogen gas which is advantageous in terms of cost is adopted.

Further, the blowing rate V _INJ [kg / min] of the dephosphorizing agent is 600 or less. Preferably, in view of the treatment time of the dephosphorization treatment, it should be as large as possible within this range. That is, for example, the blowing speed V _INJ [kg / min] is most preferably 400 to 600.

The solid-gas ratio R _INJ [kg / Nm ³ ], which is the ratio of the above dephosphorizing agent to the carrier gas, is set to 30 to 46.

  Then, the phosphorus concentration P [wt%] after the dephosphorization of the hot metal is set to 0.06 or less. The phosphorus concentration P [wt%] after the dephosphorization treatment is most dependent on the blowing amount of the dephosphorizing agent having the above composition. Therefore, in order to achieve the above target value, It is advisable to adjust the blowing amount appropriately.

<Acid delivery>
By the way, the hot metal accommodated in the kneading vehicle stays in the hot metal pretreatment facility and is slightly cooled by blowing the carrier gas. Therefore, as shown in FIG. 1 above, gaseous oxygen is sprayed onto the hot metal using an appropriate spraying lance at the same time as the dephosphorizing agent is blown, and the oxygen is reacted with the carbon component dissolved in the hot metal. Thus, the hot metal may be appropriately heated. Note that the amount of acid sent at this time is measured in advance when the temperature of the hot metal is measured before the start of the dephosphorization process, and is fixed to a certain value based on the measurement result. In this case, the temperature of the hot metal is measured and the measurement result is varied while appropriately feeding back. In the present embodiment, the former is adopted. Of course, the latter may be adopted.

  The dephosphorization process in the hot metal pretreatment facility has been described above.

  When the above dephosphorization process is completed, the hot metal is taken out from the hot metal pretreatment facility and transferred to the converter, which is the next process. In the converter, decarburization processing is mainly performed.

≪Test 1≫
Hereinafter, Test 1 for confirming the technical effect of the hot metal dephosphorization method according to the present embodiment will be described. Each numerical range described above is reasonably supported by the following confirmation test.

<< Test 1: Indicator >>
First, an index used for evaluation of each confirmation test will be described.

(Dephosphorization efficiency W [1 / Nm ³ ])
Dephosphorization efficiency W [1 / Nm ^3] refers to dephosphorization efficiency apparent per GOX 1 Nm ^3. The dephosphorization efficiency W [1 / Nm ³ ] is defined by the following formula (1).

In the above formula (1), Pi means the phosphorus concentration P [wt%] before the hot metal dephosphorization treatment, and Pf means the phosphorus concentration P [wt%] after the hot metal dephosphorization treatment. O _vol [Nm ³ ] means the amount of oxygen used in the dephosphorization treatment. “Oxygen used in the dephosphorization treatment” means the solid oxygen content in the dephosphorization agent. The amount of oxygen is converted as gaseous oxygen as indicated by the unit. Further, oxygen (so-called desiliconized oxygen content) used for oxidation of the silicon component in the hot metal is excluded from the amount of oxygen as is well known.

  The measurement of the hot metal phosphorus concentration P [wt%] is performed by a known means.

When the above dephosphorization efficiency W [1 / Nm ³ ] is less than 0.1, a large amount of dephosphorization agent and dephosphorization time are required, and the equipment capacity is reduced and the cost is increased. (Hereinafter, refer to Tables 1 and 2 below as appropriate). Further, when the dephosphorization efficiency W [1 / Nm ³ ] is 0.1 or more and less than 0.12, “− (possible)” and when it is 0.12 or more and less than 0.18, “◯ (good)”. When it is 0.18 or more, it is evaluated as “◎ (very good)”.

(Slag forming)
Slag forming relates to the presence or absence of a volume expansion phenomenon due to foaming of slag during the dephosphorization process. That is, if the slag flows out of the chaotic vehicle during the dephosphorization process, it is evaluated as “x (defective)”. If the slag does not flow out of the chaotic vehicle during the dephosphorization process, it is assumed that slag forming does not occur. Good) ”. As described above, the reason why it can be determined that no slag forming has occurred if there is no outflow is as follows. That is, when dephosphorization is performed in a chaotic vehicle, as described above, a sufficient free board cannot be secured as compared with the case where dephosphorization is performed in a converter. This is because slag is always discharged regardless of the degree of occurrence. In other words, if the slag flows out of the chaotic vehicle, it will cause damage to the auxiliary equipment of the hot metal pretreatment facility and the yield loss of iron that is caught in the slag and flows out at the same time.

(Slag adhesion)
Reference is now made to FIG. FIG. 2 is a cross-sectional view of the chaotic vehicle. In this figure, slag deposits fixed to the inner wall surface of the chaotic vehicle are schematically depicted. In this figure, “Example” and “Comparative Example” are clearly described in order to briefly explain one of the significance of the hot metal dephosphorization method according to this embodiment. That is, according to the present embodiment, as shown in the “Example”, slag does not adhere to the inner wall surface of the chaotic vehicle, and the accommodation volume of the chaotic vehicle can be secured over a long period of time. As shown in the figure, a large amount of slag adhered to the inner wall surface of the chaotic vehicle, and the accommodation volume of the chaotic vehicle gradually decreased. As a result, repair of the chaotic car was frequently required, and the life of the chaotic car itself was shortened.

  Now, with regard to the above slag adhesion, the weight of the kneading car before accepting the hot metal from the blast furnace and the weight of the kneading car after transferring the molten iron after the dephosphorization process to the converter and carrying out the specified waste work If the weight of the chaotic vehicle is increased, the slag adheres to the inner wall surface of the chaotic vehicle and is evaluated as “× (defect)”, while the weight of the chaotic vehicle is evaluated. If no increase is observed, the slag adheres to the inner wall surface of the chaotic vehicle and the slag adhesion is evaluated as “◯ (good)”. In addition, the above “removal work” means that the above-mentioned chaotic wheel is rotated in a predetermined direction to transfer the hot metal from the kneading wheel to the converter, and within about 1 to 2 hours from the time when this transfer is completed. Again, this is an operation of rotating the chaotic vehicle in a predetermined direction to discharge the slag remaining in the chaotic vehicle to the outside of the chaotic vehicle. It is added that the above-described exclusion operation is a general method for those skilled in the art.

(Clogged INJ)
INJ clogging means the presence or absence of clogging of the blowing lance. That is, when the dephosphorizing agent is blown into the molten iron together with the carrier gas, if the blowing lance becomes clogged, the dephosphorization process cannot be continued and the phosphorous concentration in the molten iron cannot be lowered to a desired value or less. On the other hand, when the dephosphorization process is completed without causing clogging of the blowing lance, it is evaluated as “◯ (good)” regarding INJ clogging.

(Temperature after treatment)
The post-treatment temperature means the temperature of the hot metal at the time when the hot metal treatment is completed, more specifically, immediately after the blowing of the dephosphorizing agent is finished and the blowing lance is taken out from the kneading vehicle. An appropriate thermocouple is used to measure the hot metal temperature. What is necessary is just to insert a thermocouple into the inside of a chaotic vehicle from the above-mentioned slag discharge hole, for example.

(Heat removal)
The heat removal amount means a value obtained by subtracting the measurement result of the hot metal temperature when the hot metal treatment is completed from the measurement result of the hot metal temperature when the hot metal treatment is started. More specifically, the time point at which the hot metal treatment is started means a time point immediately before the blowing lance is inserted into the kneading vehicle in order to blow the dephosphorizing agent into the hot metal. If this heat removal amount is 60 ° C or more, the decarburization process in the converter as the next step requires oxygen blowing or temperature rise operation by thermite reaction, which is disadvantageous in terms of cost, and in particular, the hot metal treatment is completed When the temperature of the hot metal falls below 1270 ° C., so-called skinning may occur in the hot metal, so the heat removal amount is evaluated as “x (defect)”. On the other hand, if the heat removal amount is less than 60 ° C. It is evaluated as “◯ (good)” regarding the amount of heat removal. During the dephosphorization process, the temperature of the hot metal is continuously measured, and the measurement result is fed back to the amount of oxygen supplied by oxygen spraying for heating the hot metal, thereby making the temperature of the hot metal as low as possible. If the operation is to be kept constant, the above heat removal will be almost zero. As described above, in the above-described embodiment (main test), such an operation is not adopted. Therefore, it is meaningful to evaluate the above heat removal amount. Of course, there is no particular circumstance that hinders the above-described operation to keep the temperature of the hot metal as constant as possible, and in this sense, the above embodiment is merely one embodiment. .

≪Test 1: Common test method and common test conditions≫
Next, test methods and test conditions common to each confirmation test will be described.

(Dephosphorization agent)
In this test, the dephosphorizing agent is produced by appropriately blending iron oxide, quartzite, dolomite, etc. into the calcined lime instead of blending the sintered sinter and calcined lime as appropriate. This is for the purpose of further clarifying the significance of producing a dephosphorizing agent from sintered ore as a raw material in comparison with Test 2 described later.

In this test, the average particle diameter φ _AVE of the dephosphorizing agent is set to approximately 100 μm. This is to promote the dephosphorization reaction.

(Chaos car)
A kneading vehicle that can accommodate 290 ton of hot metal is used.

(Presence / absence of acid delivery)
In order to heat the hot metal during the dephosphorization treatment, when the dephosphorizing agent is blown, the above-described acid feeding is performed at an acid feeding rate (fixed value) of about 50 [Nm ³ / min].

(Each lance)
As the blowing lance for blowing the dephosphorizing agent, one made of an alumina refractory is used. Specifically, the outer diameter is 300 mm, it is a two-hole type, the direction of the discharge hole is perpendicular to the length of the lance, the hole shape of the discharge hole is a circular straight hole, the hole diameter is 43 mm, The carrier gas is nitrogen gas.

  The spray lance for oxygen spray is made of copper alloy and water-cooled. Specifically, the outer diameter is 165 mm, the type is a two-hole type, and the direction of the discharge hole is 15 degrees with respect to the length of the lance (becomes obliquely downward). As a circular straight hole, the hole diameter is 34 mm, and the blowing gas is oxygen.

(Hot metal)
In this test, the carbon concentration of the hot metal is approximately 4.0 to 4.5 [wt%]. Further, the phosphorus concentration P [wt%] of the hot metal before the dephosphorization treatment is set to about 0.092 to 0.115.

≪Test 1: Individual test conditions and test results≫
Next, individual test conditions and test results of each confirmation test are shown in Table 1 below. In Table 1 below, the column title “Evaluation” is a comprehensive evaluation of the results of each test. Specifically, the dephosphorization efficiency W [1 / Nm ³ ], slag forming, slag adhesion, INJ A case where none of the evaluations regarding clogging, post-treatment temperature, and heat removal amount correspond to a failure is evaluated as “Good (good)”. On the other hand, a case where at least one of these evaluations corresponds to a failure is evaluated as “ X (defect) ”. In Table 1 below, “H” means the upper limit or the vicinity of the upper limit within the numerical range mentioned in the description of the above embodiment. Similarly, “M” is the center or near the center, “L” is the lower limit or near the lower limit, “↑” is out of the range, and “↓” is the range. Means that they are off the bottom.

≪Test 1: Consideration≫
(1) V _INJ
According to each test, when the blowing speed V _INJ [kg / min] exceeds 600, the evaluation regarding the dephosphorization efficiency W [1 / Nm ³ ] is poor. This is considered to be because the blowing rate of the dephosphorizing agent becomes the diffusion rate limiting of the molten steel component. It can also be seen that the dephosphorization efficiency W [1 / Nm ³ ] is almost constant at 600 or less. However, if the blowing speed V _INJ [kg / min] is too small, the evaluation regarding the dephosphorization efficiency W [1 / Nm ³ ] will be inferior, so it may be 400 or more, for example.

(2) R _INJ
When the solid-gas ratio R _INJ [kg / Nm ³ ] was less than 30, the heat removal of the hot metal in the dephosphorization process was larger than expected. This is considered due to heat removal by the carrier gas. On the other hand, when the solid-gas ratio R _INJ [kg / Nm ³ ] exceeded 46, INJ clogging occurred.

(3) CaO
When CaO [wt%] exceeded 18, evaluation regarding slag adhesion was poor. On the other hand, when CaO [wt%] is less than 14, the evaluation regarding slag forming was poor.

(4) SiO ₂
When SiO ₂ [wt%] is less than 5, the evaluation regarding slag adhesion was poor. On the other hand, when SiO ₂ [wt%] exceeded 8, evaluation regarding slag forming was poor.

(5) t. Fe
t. When Fe [wt%] was less than 48, the evaluation regarding the dephosphorization efficiency W [1 / Nm ³ ] was poor. On the other hand, t. When Fe [wt%] exceeded 55, evaluation regarding slag forming was poor.

(6) O
When O [wt%] was less than 19, the evaluation regarding the dephosphorization efficiency W [1 / Nm ³ ] was poor. On the other hand, when O [wt%] exceeded 25, the evaluation regarding slag forming was poor.

(7) C / S
When C / S was less than 2.2, evaluation regarding slag forming was poor. On the other hand, when C / S exceeded 3.0, evaluation regarding slag adhesion was poor.

(8) CaO / O
When CaO / O was 0.75 to 1.10, the evaluation regarding the dephosphorization efficiency W [1 / Nm ³ ] was generally good.

As described above, from the considerations (1) to (8), it was found that it is particularly necessary to pay attention to CaO, SiO ₂ and C / S in order to prevent slag forming and slag adhesion at the same time. In order to increase the dephosphorization efficiency W [1 / Nm ³ ] and shorten the time required for the dephosphorization process, in particular, t. It was found that attention should be paid to Fe, O, and CaO / O.

(9) CaO basic unit When the CaO basic unit [kg / ton] exceeded 20, even if C / S was low, slag adhesion gradually increased. Therefore, it is important that the CaO basic unit [kg / ton] is 20 or less from the viewpoint of slag adhesion. Moreover, 20 or less is preferable also from another viewpoint. Another viewpoint is as follows. That is, calcined lime is not only fed into the hot metal as a component in the dephosphorizing agent, but also in the decarburization process in the next converter, dephosphorization in the converter and the application of the hot metal surface. It is thrown into the hot metal for the purpose of the agent. Accordingly, the basic unit [kg / ton] of all CaO including CaO in the dephosphorizing agent is preferably 20 or less. Note that “CaO introduced into molten iron in a form not included in the dephosphorizing agent” in “all CaO including CaO in the dephosphorizing agent” includes, for example, a forming inhibitor and a desulfurizing agent. .

As described above, in the above embodiment, hot metal dephosphorization is performed by the following method. That is, the dephosphorizing agent satisfies the following composition. The CaO basic unit [kg / ton] as the total lime basic unit is 20 or less. The dephosphorization agent blowing speed V _INJ [kg / min] is set to 600 or less. A solid-gas ratio R _INJ [kg / Nm ³ ], which is a ratio between the dephosphorizing agent and the carrier gas, is set to 30 to 46.
CaO [wt%]: 14-18
SiO ₂ [wt%]: 5~8
t. Fe [wt%]: 48 to 55
O [wt%]: 19 to 25
CaO / O: 0.75 to 1.10
C / S: 2.2 to 3.0

  According to the above method, slag forming and slag adhesion can be prevented simultaneously. Further, since the efficiency of the dephosphorization process is excellent, the time required for the dephosphorization process is shortened, which contributes to the improvement of productivity. Further, when the phosphorus removal treatment is performed in the kneading vehicle, slag adhesion is prevented, so that the life of the kneading vehicle can be extended.

≪Test 2≫
Next, the test regarding the manufacturing method of a dephosphorizing agent is demonstrated. Here, it demonstrates centering on a different point from said Test 1, and it abbreviate | omits suitably about the description which overlaps with the said Test 1. FIG.

  In the above test 1, when producing the dephosphorizing agent, the sintered sinter was not used, but iron oxide, quartzite, dolomite and the like were appropriately added to the calcined lime. In contrast, test No. of this test. In 51-54, a dephosphorizing agent shall be manufactured by appropriately blending sintered ore and calcined lime (see Table 2 as appropriate). On the other hand, test No. of this test. In 55-57, it manufactured by the same mixing | blending as the said test 1.

  Table 2 below shows the individual test conditions and test results of each confirmation test in this test. In Table 2 below, the column title “sintered ore wt%” means the blending ratio of the sintered ore with respect to the entire dephosphorizing agent when using the sintered ore when producing the dephosphorizing agent. “Calcined lime” means the ratio of calcined lime to the total dephosphorization agent. Test No. In 55-57, the value of the column title “sintered ore” being zero indicates that no sintered ore is used. In 55-57, the sum of the value of the column title “sintered ore” and the value of the column title “calcined lime” is not 100 other than the sintered ore blended in the calcined lime when producing the dephosphorizing agent. It is based on the raw materials, that is, iron oxide, silica, dolomite and the like.

According to Table 2 above, when the dephosphorization agent is manufactured using sintered ore, the dephosphorization efficiency W [ It can be seen that the evaluation with respect to 1 / Nm ³ ] was good. Therefore, it is preferable to produce the dephosphorizing agent by appropriately blending sintered ore and calcined lime.

  Next, it will be considered that when a dephosphorizing agent produced using sintered ore as an iron oxide source as described above was used, good results with respect to the dephosphorization efficiency W were obtained.

  Since the sintered ore is a sintered ore having a particle size lower than the standard as described above, CaO and t. Fe is already bonded. As a result, the sintered ore has a low melting point and the hatching of the dephosphorizing agent with respect to the hot metal is good. In short, since the dephosphorizing agent produced using sintered ore is easily melted against molten iron, the dephosphorization reaction is promoted, and therefore, it is considered that good results with respect to the dephosphorization treatment efficiency W were obtained. .

  Although the preferred embodiments of the present invention have been described above, the above embodiments can be implemented with the following modifications.

  That is, for example, in the above embodiment, the dephosphorization process is performed in the hot metal pretreatment facility, that is, in a state where the hot metal is accommodated in the kneading vehicle, but instead, in the converter, that is, It is also conceivable that the hot metal is stored in a converter. However, the hot metal dephosphorization method according to the present invention is based on the assumption that the dephosphorizing agent is blown into the hot metal, and for example, the so-called upper charging operation in which the dephosphorizing agent is simply introduced into the surface layer of the hot metal. Is not intended.

Cross-sectional schematic view of a chaotic vehicle during dephosphorization treatment Cross section of chaotic car

Claims (2)

Dephosphorization of hot metal in which the phosphorus concentration P [wt%] of the hot metal is 0.06 or less by blowing a dephosphorizing agent together with a carrier gas to the hot metal having a phosphorus concentration P [wt%] of 0.09% or more. A method,
The dephosphorizing agent shall satisfy the following composition:
CaO [wt%]: 14-18
SiO ₂ [wt%]: 5~8
t. Fe [wt%]: 48 to 55
O [wt%]: 19 to 25
CaO / O: 0.75 to 1.10
C / S: 2.2 to 3.0
CaO basic unit [kg / ton] as total lime basic unit is 20 or less,
The dephosphorization agent blowing speed V _INJ [kg / min] is 600 or less,
The solid-gas ratio R _INJ [kg / Nm ³ ], which is the ratio between the dephosphorizing agent and the carrier gas, is set to 30 to 46.
A method for dephosphorizing hot metal characterized by the above. The dephosphorizing agent is manufactured by blending sintered ore and calcined lime,
A method for dephosphorizing hot metal characterized by the above.

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