JPS602611A - Desiliconizing agent mixed with light burned dolomite for treating molten iron - Google Patents

Abstract

PURPOSE:To obtain the titled desiliconizing agent consisting of iron oxide dust such as converter dust and light burned dolomite, enabling the efficient desiliconization of molten iron, and preventing resulfurization during desiliconization. CONSTITUTION:Iron oxide dust such as converter dust is mixed with light burned dolomite to prepare a desiliconizing agent 8. This agent 8 is put in a molten iron trough 4 from a hopper 7. Slag having low viscosity and a significant slag making effect is formed with the agent 8, and molten iron is efficiently desiliconized while effectively preventing resulfurization. At the same time, desulfurization is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment agent for hot metal, and more specifically, to a treatment agent for hot metal that can efficiently desiliconize hot metal and prevent resulfurization during desiliconization. Regarding desiliconizing agents.

Regarding the desiliconization treatment of hot metal, iron oxide-based sintered ore is added to the hot metal.
A method of adding dust or the like is conventionally known.

However, in the case of this method, the basicity (Oak/Sin, ) of the desiliconized slag decreases significantly during desiliconization treatment, and
a) This reacts with the desulfurization slag adhering to the inner surface of the torpedo or hot metal ladle to form slag with a significantly high S concentration, resulting in a significant increase in S in the hot metal due to the slag-hot metal reaction, resulting in This was causing a major hindrance to the process after desiliconization.

One way to deal with this problem is to use lime as a basicity regulator, but even with this method, if a large amount of lime is added, the viscosity of the desiliconized slag will increase significantly, so it will not turn into slag. First, it has the disadvantage of having almost no desulfurization ability.

Therefore, the present inventors conducted extensive research to eliminate these drawbacks, form a desiliconizing slag with low viscosity, and prevent resulfurization during desiliconization. It has been discovered that by adding light calcined dolomite as an agent, simultaneous desiliconization and desulfurization can be carried out extremely effectively. It is characterized by the fact that it was made possible.

The present invention will be explained in detail below.

Any suitable iron oxide-based dust can be used as the desiliconizing dust, but in order to prevent slag generation as much as possible, it is preferable to use dust with as much iron oxide as possible, and this point should be taken into account. Then, converter dust is (i) inexpensive, reduces dust treatment costs, and (i)
i) Contains iron oxide at a high content of 70 to 90%, and is therefore suitable. Table shows examples of components of converter dust.
Shown in 1.

In addition, if the iron oxide content is less than 70%, only the amount of slag generated increases and the desiliconization efficiency decreases, which is not desirable.

Noke using lightly calcined dolomite as a basicity regulator,
From the analysis results of various experimental examples described below, (i) the viscosity of desiliconized slag can be significantly lowered compared to when lime is used;
(ii) The content of OaO and MgO is approximately 60% and 80%, respectively, so the basicity is high, and even compared to lime-based materials, sufficient desulfurization ability can be expected. It's for a reason. Table 2 shows examples of the components of light calcined dolomite.

Table 2 (Part 2) Note that dolomite (xgco8) is not preferred as a basicity regulator because it lowers the CO2 source by the amount of hot metal temperature due to an endothermic reaction.

As in the present invention, lightly calcined dolomite)'I as a basicity regulator
When F- is used, the desiliconizing slag has better slagability than when lime is used as in the past, and this has been found through experiments by the present inventors. That is, desulfurization ability is generally expressed by the following formula.

However, (S): S concentration in slag [S]: S concentration in hot metal Os: Sulfite capacity Po2: Oxygen partial pressure (atm) T: Temperature (°C) log Os −-5,54+ 1. ;15 A...
・・・・・・・・・・・・・・・(2) OaO As can be seen from the above formula, Aca. The higher the sulfide capacity (ie, sulfide capacity), the more advantageous is desulfurization. In this respect, from the relationship of equation (8), in terms of chemical reaction, (%a
Lime is advantageous due to the difference in function between aO) and (%MgO), but physically, the slag status (viscosity) of desiliconization slag
was a problem, and the following experiment was conducted to find out which is more advantageous: lime-based or lightly calcined dolomite.

That is, as a desiliconizing agent, a mixture (a) of converter dust 20J19/l-p and light calcined dolomite) 101119/l-p, converter dust 20''9/l-p and lime 10 kg/
Two kinds of mixtures (b) of t-p were prepared and added to hot metal, and the S soil in the hot metal was changed from 0.40% to 0.0% by desiliconization reaction.
The composition of each slag was analyzed when it was reduced to 10%.

Part (4) The results are shown in Figure 1.

The figure shows the OaO-MgO-5in2(7) isoviscosity line (1
500°C, poise, (I, I, Cu1t' y
This is a partial representation of the triangular diagram, and the slag composition is calculated.

As can be seen from the figure, the MgO content of the slag using mixture (a) is 20% and the slag viscosity is about a poise, whereas the slag viscosity when using the mixture (b) which does not contain MgO is 50%. 0 exceeding poise
Therefore, in terms of slag slag formation, it is significantly more advantageous to use lightly calcined dolomite containing MgO.0 (Example) A desiliconization agent consisting only of converter dust.

Eight types were prepared, including one in which converter dust was mixed at a ratio of eight parts to one part lime, and one in which light burnt dolomite was mixed in various ratios to converter dust, and as shown in the desiliconization flow in Fig. 2,
These desiliconizing agents 8 are transferred to the hopper 7 in a 4000 m° class blast furnace 1.
Desiliconization treatment was carried out by pouring the hot metal into the branch trough 4. In addition, in the same figure, 2 is the hot metal gutter, 8 is the skimmer, 5 is the tilting trough, 6 is the tobedo, (a) is the hot metal sampling position before the desiliconization process, and (b) is the hot metal sampling position after the desiliconization process. When using a desiliconization agent consisting only of T0 converter dust, as shown in Fig. 8, if a large amount of converter dust is introduced, the Si reduction width ΔSi (before and after desiliconization treatment) will naturally change. (difference in Si content) increases, and Si content decreases significantly. However, in relation to desulfurization, as shown in Figure 4, as ΔSt increases (that is, as the input amount of converter dust increases), the S
The decrease width ΔS (the difference between the S content before and after the desiliconization treatment) becomes smaller, and the increase in the S content in the hot metal becomes more likely.

As mentioned above, this increase in the S content in the hot metal is a phenomenon caused by the reaction between the desulfurization slag in the torpedo and the desiliconization slag. When light calcined dolomite was used in combination, it was found that as the mixing ratio of light calcined dolomite was increased by 3, the increase in S during desiliconization could be prevented, and conversely, the desulfurization effect could also be exerted at the same time. I found it.

The experimental results are shown in FIG. This shows that when the mixing ratio of light burnt dolomite to converter dust is about 30 or more, the effect of preventing resulfurization can be obtained and the effect of desulfurization can also be expected.

On the other hand, when desiliconizing agent 2 containing lime was used in converter dust, it was found that the desulfurization ability decreased (i.e., the desulfurization ability of the converter dust was approximately 80%). A desiliconizing agent (A) mixed in a ratio of 8:1 and a desiliconizing agent (A) mixed with converter dust and lime in a similar ratio of 8:1
B) was compared with the desiliconizing agent (0) containing only converter dust, and as shown in Figure 6, when lime was mixed (B), the desiliconizing agent containing only converter dust ( Compared to C), although it is possible to prevent the increase in S content in the hot metal and resulfurization, there is a clear decrease in desulfurization ability compared to (A) when lightly calcined dolomite is mixed as in the present invention. It will be done.

This is because, as already mentioned, lime-based materials have a high sulfide capacity, but have a high viscosity, resulting in poor slag formation and low desulfurization ability.

As is clear from the above detailed description, since the present invention mixes lightly calcined dolomite with converter dust and uses it as a desiliconizing agent, it forms a slag with low viscosity and good slagability. The effect is remarkable because it can effectively prevent resulfurization during desiliconization, and at the same time enable desulfurization and efficiently accomplish desiliconization.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the composition and viscosity of desiliconized slag.
Triangular diagram of isoviscosity lines for O-MgO-5in2 (
Figure 2 is a schematic explanatory diagram showing the desiliconization flow, Figures 3 and 4
The figure shows ΔS when conventional desiliconizing agent (converter dust) is used.
i1 ΔS, FIG. 8 shows the relationship tAE between the desiliconization unit and ΔS soil, and FIG. 4 shows the relationship between ΔSi and ΔS in the case of FIG. 3. Figure 5 shows the relationship between the mixing ratio and ΔS when a mixed desiliconizing agent of converter dust and light calcined doloma (8)ite according to the present invention is used, and Figure 6 shows the relationship between ΔSi and ΔS compared to the conventional method. This is a diagram showing a comparison between a desiliconizing agent and an embodiment of the present invention. 4. Hot metal branch trough 6. Dobby door hopper 8. Desiliconizing agent. Patent Applicant Kawasaki Steel Corporation Figure 1 MyO (wt%) Figure 2 Figure 3
Figure (nra) S'l/ (U6n gI7

Claims (1)

[Claims] L A desiliconizing agent for hot metal treatment characterized by being made of a mixture of iron oxide dust and lightly calcined dolomite.