SU1260397A1 - Method of dressing steel-melting slag - Google Patents

Description

The invention relates to ferrous metallurgy and can be used but in the processing of steelmaking material.

The purpose of the invention is to increase the degree of separation of the iron-containing part of the slag.

When the slag melt crystallizes, crystals of silicates with solid solutions of PjOg are first formed, the density of the crystals is less than the liquid matrix, and at low viscosity of the liquid phase they can float to the upper horizons. Thus, two factors contribute to the dilution of pshak with the enrichment of the lower layers with iron oxides: the intense precipitation of silicate crystals and the low melt viscosity. However, these conditions are mutually opposite in temperature conditions: at large supercooling, the high intensity of the precipitation of crystals is silicate but the viscosity of the liquid phase, which slows down the formation of the formed crystals. During slow crystallization, the viscosity increases with an increase in the intensity of the formation of primary crystals, so d-even when repeating the cycle several times additionally, only a small part of the previously formed crystals emerges, mainly for short distances. As a result, the lower layers of slag are little enriched in iron oxides.

The essence of the invention consists in combining both of the above conditions, which facilitate efficient slag separation by local (local) overheating of the zone of relatively small width (vertical): from the temperature at which a high intensity of the crystals is observed to the temperature, at which the viscosity of the liquid phase is low, but there is still some undercooling and crystal formation processes are not inhibited. Thus, in such an overheating zone, the crystals formed can quickly quickly emerge, in relatively large quantities. Since the superheat zone moves slowly from top to bottom, the crystals that were previously formed move upwards by a distance approximately equal to the width of the zones. Above the overheating zone is slow cooling.

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of the previously overheated zones and in them for some time the sufficiently low viscosity of the liquid phase remains, which allows crystals to continue to float outside the descending superheat zone. In addition, during such slow cooling, the process of additional precipitation of silicate crystals, which did not stand out during primary cooling, is underway. They also have time to ascend a certain distance, increasing the separation efficiency. When repeating the processing cycle, the surface emerges again to a height of 2-3 zones as crystals separated from the first cooling (previously raised by 2-3 zones) and additionally separated crystals in the zone of the 2nd cooling, as well as to some extent the emergence of the newly released crystals during the 3rd cooling of the crystals. Similar processes occur with repeated repetition of the processing cycle. As a result, an almost complete separation in the lower layers of crystallizing silicates from the liquid phase, significantly enriched in iron oxides, is achieved.

When overheating after reaching the temperature below the solidification temperature, the intensity of the crystal cleavage additionally increases slightly and the efficiency of the subsequent overheating increases insignificantly, and the cost of heating in. links with lower melt temperatures increase. At the onset of overheating above the temperature of 120 ° C, the intensity of the separation of the crystals is still not high enough, and the viscosity of the liquid phase is still low and the overheating does not increase the speed and number of the emerging crystals. When the zone is heated to a temperature of less than T 150 C, the decrease in viscosity is small and the rate of the rise of silicates increases non-existent, and the processing process becomes ineffective. When the zone is heated to a temperature higher than the solZ, no further significant decrease in viscosity is observed and a further increase in the efficiency is insignificant, since the rate of popup does not increase, and the cost of heating significantly increases.

As mentioned above, with one processing cycle of the proposed method, there is an almost complete upwelling of previously leached crystals to a height of about 2-3 superheating zones, and the smaller the zone, the smaller the additional float zone. Therefore, with a zone width of less than 5% of the height, the process efficiency is significantly reduced. On the other hand, for the same reason, an increase in the width of the overheating zone by more than 20% of the height does not lead to a further noticeable increase in the concentration of iron oxides in these lower layers, while at the same time non-opaque. the heating costs are rising and the process becomes more expensive

With a lowering rate of the overheating zone of more than 150 mm / min, the silicates do not have time to float in the overheating zone, this leads to a sharp decrease in the efficiency of separation. At a speed of less than 50 mm / min, the amount of floating silicates practically does not increase, and the process is unnecessarily delayed, besides, because of the rest of the shpak mass, heating costs increase, and the slag separation efficiency remains almost unchanged.

Repetition of the cycle for more than four times does not give a further increase in the efficiency of separation, since after the fourth 1cm from the lower iron-containing part almost all the mass of silicates that can be removed from the Bosle melt is removed.

180 200 210 190 240 120

The following cycles only increase the heating and slow down the process.

Example. 250 kg of shpak composition,%: CaO 46.3; SiO 18.3; FeO 21.4 P O .2.4 was poured into a cylindrical metal container with a height of 1 m at 1550 ° C. After cooling to 1420 s, an annular inductor with a height of 10 cm was brought to the tank from above and, due to induction heating, the slag temperature in the heating zone was raised to 1470-1490 ° С, while the inductor was lowered at a speed of 50 mm / min, and after lowering to the lowest point it was raised and lowered again at a speed of 50 mm / min. The cycle was repeated three times. As a result, the FeO content in the lower part of the slag monolith was 52.3%, and in the upper part, 6.5%.

The table shows the results of experiments carried out in accordance with the invention in order to substantiate the proposed limits of technological parameters. Chemical composition of slag before processing,%: FeO 21.4; ,four;

Cao 46.3; SiO, j 18.3. Solidus temperature, liquidus temperature 162 (C.

The economic effect is achieved due to the sale of slag as an iron-containing material in the blast-furnace production, as well as through the sale of the phosphorus-containing part of the slag (when processing fosfat-1lshaka) as a fertilizer in agriculture.

42.3

48.8

49.1

47.5.

34.6

35.8

Table continuation

Claims (1)

METHOD FOR ENRICHING STEEL Smelter, including multiple heating of the slag layer above the liquidus temperature, aging and cooling, subsequent separation of the iron-rich portion of the oxides, characterized in that, in order to increase the degree of separation of the iron-containing part of the hairpin, after cooling to a solidus temperature of 80-120 ° C heating is carried out in a zone with a width of 5-20% of the total height of the slag layer to a solidus temperature of 150-250 ° C, while. the heating source aeons many times i move from top to bottom with speed _e 50-150 mm / min, SS