JPS5855205B2 - How to process molten iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing impurity elements from molten iron, and particularly a method for performing desulfurization, desulfurization, and dephosphorization of molten metal simultaneously or one after another in a single molten iron transport container. Regarding.

For example, a pretreatment of hot metal that has been generally carried out in the past is a desulfurization treatment carried out in a hot metal pot or a torpedo car.

On the other hand, in order to improve the operational performance of steelmaking furnaces, attempts have recently been made to further perform dephosphorization treatment at the hot metal stage.

However, in order to carry out the dephosphorization reaction at the hot metal stage, it is necessary to reduce the Si% in the hot metal to a level below 0.15%. is impossible.

(Fig. 1), therefore, in the first step, desulfurization treatment is carried out using acidic slag under an oxidizing atmosphere to completely eliminate the desulfurization slag, and then desulfurization treatment is performed using basic slag under a reducing atmosphere. Alternatively, a two- or three-stage treatment method must be used in which dephosphorization treatment is performed using basic slag in an oxidizing atmosphere.

By the way, unless these treatments are carried out in a continuous treatment tank (in which the molten metal is continuously flowing), each reaction must be carried out separately in multiple stages.

For this reason, the processing time for the reaction becomes longer, which inevitably causes a drop in the temperature of the hot metal, resulting in a temperature loss.In addition, iron flows out due to the slag after each reaction, which causes many problems in industrialization. .

Also, hot metal with sufficiently low Si content (Si 0.15% or less)
There is no need for desulfurization treatment, but Na2C
Simultaneous desulfurization and dephosphorization with O3-based, CaO-based treatment agents, etc.
For the Na2CO3 system, the desulfurization reaction progresses satisfactorily, but the dephosphorization reaction is inferior (Fig. 3), while for the CaO system, the dephosphorization reaction progresses satisfactorily, but the desulfurization reaction is inferior (Fig. 2).
.

Therefore, if it is desired to sufficiently remove sulfur phosphorus, it is necessary to carry out a two-step process of, for example, carrying out a treatment mainly consisting of desulfurization, then draining the slag, and then carrying out a dephosphorization process, which makes the work complicated.

The present invention was made to solve these difficulties, and its gist is that the surface layer of molten iron stored in a single container for transporting molten iron is divided into various types by one or more partition walls. The purpose is to remove a plurality of impurities in a single container by injecting different refining agents into each tank.

The present invention will be explained in more detail below.

When removing Si, P, and S from hot metal, especially when removing P, the removal efficiency is poor unless the Si content in the hot metal is 0.15% or less.

Therefore, when Si in hot metal is 0.15% or more and when Si is 0.15% or more,
The case of 15% or less will be described.

1. When Si in hot metal is 0.15% or more.

As shown in Fig. 4, first, iron oxide or oxygen gas necessary for desulfurization is injected as a refining agent from lance 1.
Desulfurization treatment is performed until the Si content of the hot metal in the pig iron mixer 4 becomes 0.15% or less, centering on the tank.

Next, lance 2 was used to desulfurize, and as a dephosphorizing agent: Na 2C
O3 + iron oxide, or CaO + CaF2 + iron oxide + CaC
Inject t2 to lower P and S to the target level centering on tank B.

At this time, if you want to make P and S particularly low, CaC2jCa
A strong desulfurizing agent such as O or a scleral phosphor is injected mainly into tank C to obtain the target hot metal component.

2. When Si in hot metal is 0.15% or less.

As shown in FIG. 5, a desulfurization and dephosphorization agent such as Na2CO3+iron oxide, etc., or Cao+CaF2-) Cact2+iron oxide, etc. is injected from the lance 2 mainly into tank B.

At the same time as this treatment, or subsequently, using lance 3, CaC2, Na2CO3, which has a large desulfurization ability,
Alternatively, CaO + iron oxide, etc., which have a large dephosphorizing ability, are injected into the center of the C tank.

In the above method, 5 is a partition wall in both FIGS. 4 and 5.

If the part of this partition wall that is immersed in the hot metal is too short, the refining agent reactant (slagnia a) will occur.

b, c,) come out through the lower part of the partition wall, so the immersion depth must be at least 20% of the hot metal depth, and 70
% or more, mutual stirring and diffusion of the hot metal becomes insufficient, which is not preferable.

The arrangement of the partition walls is determined depending on how many types of refining reactions are to be carried out, but it is preferable to use a double partition wall rather than a single partition wall in order to prevent mixing of the refining reaction products.

Although the above description has been made regarding the treatment of hot metal, it goes without saying that the treatment of molten steel can be carried out in the same manner using a suitable refining agent.

Next, an example will be described.

Example 1 4.5% C and 940% 5iO were added to the pig iron mixing car 4 (capacity 300 t) shown in FIG. 6, which had a single partition wall 5 arranged inside.
250 TON of hot metal containing 0.40% Mn, 10% Po, and 80.03% was received.

The immersion depth of the partition wall in the hot metal is 30% of the hot metal depth.

First, for A test, 5Nm of oxygen gas was passed through immersion lance 1.
T-P and iron ore powder 25Ky/T-P were injected for 10 minutes to reduce the Si content in the hot metal to 0.10%.

Next, for B measurement, Na2Co315Kt/T-P and iron ore powder 5Ky/T-p were mixed with oxygen gas through lance 2 for 15 minutes.
I blew it for a minute.

The hot metal components after treatment are C4,0%, SiO,05%, Mn.
0.20%, po, 0.15%, and SO, 0.007%, and sufficient desulfurization, dephosphorization, and desulfurization could be carried out.

Example 2 C4.3%, Sio, io%, M
n 0.3%, Po, 12%, So, 04% hot metal 1
50 TON of pig iron was received.

The immersion depth of the partition wall 5 in the pig iron was 20% of the hot metal depth.

First, for B measurement, CaO powder 15Ky/T-P, CaF2
2KP/T-P, CaC21Ky/T-p, scale powder 20Kg/T-P was blown in with nitrogen gas through lance 2 for 10 minutes, and at the same time CaC21Kp/T-P was added for C measurement.
T-P was blown with nitrogen gas through lance 3 to obtain the following extremely low phosphorous and sulfur hot metal.

Hot metal components after treatment C3.7%, SiO, 02%, M
n0.20%, PO,005%, SO,002
%, Example 3 25 with double partition wall 5.5 arranged inside as shown in FIG.
0T pig iron mixer 4 with C4.6%, Si 0.6%, Mn
0.5%, Po, 11%, 80.05% hot metal23
0TON was received.

The immersion depth of the partition wall 5.5 in the pig iron was 50% of the hot metal depth.

Oxygen gas and iron ore powder are blown into tank A to remove Si in the hot metal.
was desulfurized to 0.05%, and a large amount of desulfurization slag was generated at the top of tank A, which was removed using a slag suction device.
Next, add 2Ky/T-P of CaC2 to tank C and Ca0 to tank B.
15 Kp/T-P, iron ore 10Ky/T-P.

CaF23Ky/T-P powder was simultaneously blown with nitrogen gas, and a desulfurization treatment was carried out in tank C and a treatment mainly consisting of dephosphorization in tank B, resulting in the following extremely low phosphorous sulfur hot metal.

Hot metal components after treatment C3.5%, Si0.03%, Mn0
．． 30%, PO, 005%, SO, 005%, Example 4 4.1% C, 0.08% Si in the pig iron mixing car 4 (capacity 200T) equipped with a single partition wall 5 inside as shown in FIG.
, Mn 0.25%, Po, 150%, So, 035
200TON of hot metal was received.

The immersion depth of the partition wall 5 in the pig iron was 25% of the hot metal depth.

Using one nozzle 1 with protruding holes on the left and right sides, Ca013 KP/T-P was measured from the protruding holes of B measurement.

CaF 21.5K! iL/TP, Cac
A210 Ky/TP to iron ore powder 25Kp/T
-P is blown in with nitrogen gas, and at the same time CaO5Ky/T-P is injected from the protruding hole on the C tank side.

At powder 0.3 Kp/T-P was blown in with nitrogen gas to obtain the following extremely low phosphorous sulfur hot metal.

Hot metal components after treatment C3, 9%, SiO, 02%, Mn0
．． 20%, PO, 010%, 80.007%.

As described above, the present invention is an industrial invention that can perform the desulfurization, desulfurization, and dephosphorization reactions simultaneously or sequentially using the same storage container, and achieve effective results together. .

[Brief explanation of drawings]

FIG. 1 is a graph showing the dephosphorization reaction by Na2COa,
Figures 2 a and t) are graphs showing simultaneous dephosphorization b and desulfurization a reactions using a CaO-based treatment agent; Figures 3 a and b are graphs showing simultaneous desulfurization a and dephosphorization reactions using a Na2CO3-based treatment agent; Fig. 4 is an embodiment of the present invention when Si in hot metal is 0.15% or more, Fig. 5 is an embodiment of the invention when Si in hot metal is 0.15% or less, Figs. Figure 1, No. 8
9 are diagrams of embodiments 1, 2, 3, and 4, respectively. 1.2,3... Injection lance, 4.
...Pig-mixing car, 5...Partition wall, 6...
...Hot metal pot, A. B, C... Separate tanks.

Claims (1)

[Claims] 1 The surface layer of molten iron stored in a single container for transporting molten iron is divided into various types by one or more partition walls, and a different refining agent is injected into each divided tank to remove multiple contained impurities into a single container. A method of processing molten iron that is removed inside the chamber.