JPS6115126B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for recovering Fe and Mn in converter slag. As is well known, a large amount of converter slag is generated during refining work in a pure oxygen top-blown converter, and this converter slag contains a large amount of impurity elements such as phosphorus (P), so it contains Fe, Mn, etc. Despite containing large amounts of valuable elements, it has usually been used in landfills. By the way, as mentioned above, converter slag contains various elements, and methods have begun to be proposed to effectively utilize them. No method has been proposed. As converter slag contains large amounts of Fe and Mn as shown in Table 1, the present inventors researched techniques for economically recovering these materials, and as a result, developed the method of the present invention. By adding 100kg or less of granular converter slag per tonne of hot metal to the hot metal and stirring, the Si in the hot metal reduces the iron oxide and manganese oxide in the converter slag, making the process so that the Si content in the hot metal is 0.02% or more. The gist of this paper is a method for recovering Fe and Mn from converter slag, which is characterized by completing the following steps.

[Table] Now, the present invention will be explained in more detail below. When granular converter slag is added to hot metal and stirred, FeO and MnO in the converter slag are converted to the following by Si in the hot metal.
It is reduced as shown in equations (1) and (2). 2FeO+Si→SiO ₂ +2Fe ...(1) 2MnO+Si→SiO ₂ +2Mn ...(2) Therefore, Fe and Mn in the converter slag will be dissolved in the hot metal and recovered. One of the reasons why the amount of granular converter slag is limited to 100 kg or less per tonne of hot metal is that if more is added, Mn in the hot metal will turn into slag due to the reaction of the following equation (3), which is undesirable. Mn + FeO → MnO + Fe ... (3) In other words, not only is the Mn in the converter slag not recovered into the hot metal, but the Mn in the hot metal turns into slag. According to the knowledge of the present inventors, it is necessary to make the amount of Si in the hot metal 0.20% or more after the reaction according to the above formula (1) in order to recover Mn in the hot metal. Furthermore, if more than 100 kg of converter slag is thrown into the hot metal, the temperature of the hot metal will drop too much, causing problems in the refining of the hot metal. Next, the reason why the converter slag is made into granules will be explained. In the present invention, it is not preferable to add converter slag in a molten state. The reason for this is that at such high temperatures, as shown in Figure 6, the oxidation reactions of Si and Mn are too close, and the reaction between hot metal and converter slag is fast, so Mn in the hot metal turns into slag at the same time as Si. This is because the object of the present invention cannot be achieved. That is, one of the features of the present invention is that solidified converter slag is used, and large lumps of the solidified converter slag are crushed into coarse or fine particles with a diameter of 30 mm or less for easy addition. By this means, the reaction with the hot metal is carried out relatively slowly, and the reaction shown in equations (1) and (2) above causes the conversion of the converter slag.
The feature is that Fe and Mn are reliably recovered in hot metal. The reason for using the above-mentioned solidified converter slag will be explained in further detail. Another feature of the present invention is to utilize the difference in melting point between the mineral phase of the solidified converter slag, that is, the 2CaO/SiO ₂ phase containing P, and other phases to dissolve the 2CaO/SiO ₂ phase as much as possible. By melting other phases that do not contain P without using P, and by the reaction of equations (1) and (2) as described above,
The point is to reduce FeO and MnO and recover Fe and Mn. In other words, as a result of observing the solidified structures of many converter slags, the present inventors found that the solidified structures of converter slags mainly appear gray plate-like or granular, and have a relatively low melting point, as shown in the micrograph in Figure 1. It separates into a phase mainly composed of high calcium silicate (hereinafter referred to as the CS phase for convenience of explanation) and a phase that appears white and has a high content of iron oxides (hereinafter referred to as the CF phase). Note that the black portion in FIG. 1 is also pores or other phases (hereinafter referred to as EP phase). Figure 2 shows the EPMA structure shown in Figure 1 above.
This shows the results of line analysis using an Electron Probe Micro Analyzer (Electron Probe Micro Analyzer). It can be seen that the CS phase is mainly composed of calcium silicate containing P ₂ O ₅ as a solid solution, and the CF phase has less P ₂ O ₅ and is oxidized. It can be seen that it is a phase with a low melting point that contains a lot of iron and manganese oxide (MnO). In this way, the converter slag usually has the CS phase and the CF phase.
The idea of the present invention was obtained from the fact that although the phases are arranged in a mixed manner, the two phases are clearly separated. Converter slag has a composition range as shown in Table 1 above. Among the above compositions, CaO, SiO ₂ ,
Iron oxide (in this invention, it is referred to as iron oxide including FeO and Fe ₂ O ₃ ) and MnO account for more than 80% of the total composition, so it is considered that the behavior of converter slag is determined by these compositions. good. Among these five compositions, CaO, SiO ₂ , and FeO (or Fe ₂ O ₃ ) are the main compositions, so converter slag is generally CaO−SiO ₂ −FeO, which is used as a phase diagram showing the behavior of converter slag. system or CaO− _SiO2
−Fe ₂ O ₃ It can be thought of as following the ternary system phase diagram. However, CaO−SiO ₂ −FeO or CaO−SiO ₂
-Fe ₂ O ₃ Since it is not a pure ternary system, we will perform the following conversion and use the CaO′-SiO ₂ ′-FeO′ system phase diagram shown in Figure 3 A and B as a pseudo-ternary system phase diagram. Explain the behavior of CaO' (%)=CaO%/CaO%+ _SiO2 %+FeO%+ _{Fe2O3 %} +MnO%×100......(1) SiO2 _' (%)= _SiO2 %/CaO%+ _SiO2 %+FeO%+Fe ₂ O ₃ % + MnO % × 100 (2) FeO' (%) = FeO % + Fe ₂ O ₃ % + MnO % / CaO % + SiO ₂ % + FeO % + Fe ₂ O ₃ % +
MnO%×100 (3) Here, MnO was added to FeO′ because MnO is enriched in the same phase as iron oxide, as shown in FIG. Also, the reason why the CaO-SiO ₂ -Fe ₂ O ₃ system was used as the standard in Figure 3 A and the CaO-SiO ₂ -FeO system in Figure 3 B was based on the composition of the converter slag. Among iron oxides, if Fe ₂ O ₃ is large, the third
This is because the converter slag according to the present invention can be clearly identified by using A in the figure as the standard, or B in FIG. 3 when FeO is large. Therefore, there is no significant difference in the basic behavior of the converter slag shown in the phase diagrams in Figure 3 A and B. Now, when the converter slag with composition B in Figure 3A is remelted, the CF phase rich in iron oxide and MnO starts to melt at 1195℃, and the line connecting composition B and 2CaO/SiO ₂ starts to melt. The CF phase completes dissolution at approximately 1400°C, indicated by point C, and the CS phase containing P ₂ O ₅ as a solid solution begins to dissolve at this temperature, and the CS phase, that is, the slag, is completely dissolved at approximately 1750°C, indicated by point B. It will be dissolved in When the CaO'-SiO ₂ '-FeO'-based converter slag shown in Figure 3B is remelted, the CF phase rich in iron oxide and MnO dissolves first, as in Figure 3A. The CS phase begins to dissolve after this has completed dissolution. In addition, the converter slag in the shaded areas D and D' in Fig. 3 A and B contains CaO solid solution, in addition to the CF phase and CS phase shown in the photograph in Fig.
The mere presence of 3CaO・SiO ₂ separates the CF phase from the redissolution.
The dissolution behavior of the CS phase is similar to that described above.
In other words, as shown in Figure 3 A and B, the CF phase of the converter slag, which is rich in iron oxide MnO, contains P ₂ O ₅ as a solid solution.
Melting point is lower than CS phase. As mentioned above, the present invention takes advantage of the difference in melting point between the CF phase and the CS phase, and is characterized by introducing converter slag in the hot metal to cause the CF phase to react with the hot metal, while preventing the CS layer from reacting as much as possible. That is. Typically, the temperature of hot metal during tapping from the blast furnace and charging into the converter ranges from about 1550 to 1250°C. In this temperature range, on the relatively low temperature side (1450 to 1250°C), the amount of CS phase in converter slag that dissolves is small, and in some converter slags, the CF phase does not completely dissolve. Therefore, when converter slag is poured into hot metal in this low temperature range, the CF phase with a low melting point melts and reacts with Si in the hot metal, reducing FeO and MnO and transferring them into the hot metal. is removed from the hot metal, and the valuable components in the converter slag are recovered into the hot metal. When FeO, MnO, etc. in the slag undergo reduction and exit from the system, dissolution of the CS phase becomes even more difficult. Therefore, the amount of CS phase with a high melting point dissolved is small, and the amount of P transferred into the hot metal is small. Moreover, since the Si content in the hot metal is decreasing, the basicity of the slag increases even if the amount of CaO charged in the converter is small, making it difficult to work in the converter to remove the P that migrates into the hot metal at this time. There is no need to worry about getting tired or increasing costs. Examples based on the above concept will be shown below. Example The converter slag shown in Table 2 was crushed to 5 mm or less,
As a result of pouring into hot metal and stirring with nitrogen gas for 15 minutes, as shown in Tables 2 and 3, the
Fe and Mn are recovered, and Si in the hot metal is removed.

【table】

[Table] As shown in the above examples, it is clear that valuable components in converter slag can be recovered by the method of the present invention. In this example, the converter slag was crushed to 5 mm or less, the input unit was 25 kg/t, the pig hot metal temperature was 1350°C,
Although the temperature was set at 1400℃, the present invention has a temperature of 100Kg/t・
The limit is pig. Now, considering the reaction efficiency, the particle size of the converter slag to be charged is better to be small, but depending on the feeding method, it may become scattered as dust, so a particle size of 30 mm or less is desirable, and the feeding unit consumption is It should be determined by the composition of the test slag and the temperature of the hot metal, the amount of P transferred to the hot metal, and the amount of temperature reduction of the hot metal.
A temperature of 50 Kg/t·pig or less is desirable, and the temperature of the hot metal should be set in consideration of the amount of P transferred to the hot metal and the temperature drop due to the addition of slag, and is preferably about 1300 to 1450°C. The method of charging and stirring the converter slag is as shown in Fig. 4 (a).The converter slag 5, 5' is crushed from the hopper 4, 4' to the hot metal 3, 3' in the torpedo car 1 or the hot metal ladle 2 in Fig. 4 b. and stirred by the nitrogen blowing lance 6 or the movable impeller 7.
Further, in the case of finely pulverized converter slag, nitrogen gas or the like may be blown into the slag. These stirring means should be selected arbitrarily. Next, the following Tables 4 and 5 show the results of converter refining using hot metal after recovering Fe and Mn by the method of the present invention.

【table】

[Table] As is clear from Table 5, Si in hot metal decreases,
Even if P increases, there is no effect on refining in the converter. By the method of the present invention, the Mn in the hot metal increases, which improves the blowstop Mn slightly and reduces Fe in the subsequent process.
-Good results have been obtained in that the amount of Mn input can be saved. In addition, as shown in Figure 4 B above, after the addition and stirring of converter slag in the hot metal ladle 2 is completed, the
As shown in the figure, the slag is removed by employing known slag removal means, such as tilting the hot metal ladle 2 and scraping out the slag 9 with a slag scraping device 8. As described in detail above, the method of the present invention provides an economical method for recovering useful elements such as Fe and Mn from converter slag.

[Brief explanation of the drawing]

Figure 1 is a micrograph (200x magnification) showing the solidification structure of converter slag, Figure 2 is a graph showing the results of line analysis by EPMA, Figure 3 A and B are CaO-SiO ₂ -FeO
and a pseudo-ternary system phase diagram related to CaO-SiO ₂ -Fe ₂ O ₃ , Fig. 4 A and B are schematic explanatory diagrams of the addition and stirring procedure for converter slag, and Fig. 5 is an explanatory diagram of the procedure for scraping out the slag.
FIG. 6 is a graph showing the standard free energy of formation of iron oxide and P ₂ O ₅ . 1: Torpedo car, 2: Hot metal pot, 3,3':
Hot metal, 4, 4': hopper, 5, 5': converter slag, 6: lance, 7: impeller.

Claims (1)

[Claims] 1 Add granular converter slag to hot metal at 100kg per tonne of hot metal.
Fe in the converter slag is characterized by reducing iron oxide and manganese oxide in the converter slag with Si in the hot metal by adding and stirring the following, and completing the treatment when Si in the hot metal is 0.20% or more. , Mn recovery method.