SU1134607A1 - Method for preparing metal charge for steel smelting - Google Patents

Abstract

1. METHOD FOR THE PREPARATION OF A METAL CHARGE steelmaking, comprising treating the liquid iron slag purged toplivnokislorodnym submersible combustion flame of tlichayuschiys in that, for the purpose povppeni efficiency of refining iron sulfur, iron temperature and efficiency of the steelmaking process, the slag flushed oxygen torch toshtivno- to 1700-1900 C and mix it with iron in the amount of 50-150% of the mass of iron. 2. The method according to p. 1, I differ u and with the fact that the iron is mixed with scrap in the amount of 4.4-7.2% of the mass of iron for every 100 ° C of its overheating. (L

Description

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A) The invention relates to ferrous metallurgy and can be used in the production of iron and steel. There is a known method of preparing to the slab in the steelmaking unit of the metal of the highest charge (iron and scrap), for example, by heating it with burners lj. This method allows to improve the technical and economic indicators of steelmaking, one at the same time making high demands on the quality of pig iron. The closest to the proposed technical essence is the method of refining liquid iron with desulfurizing slag melt previously regenerated in a ladle using G21 air or a submerged oxygen-oxygen torch Sj. . However, this method does not allow to remove large amounts of sulfur from the iron and to produce it simultaneously with the desulfurization of the iron and its heating due to the very small specific mass of slag (5-6% by weight of the iron), found in the steel processing method with synthetic slags. Research has shown that it is for these reasons that slag, as a result of the treatment of the iron, acquires a temperature close to that of the iron (1300-1400 ° C), at which its liquid mobility is at a very low level. When such slag is regenerated by blowing a torch, the degree of dispersion of the latter into the melt is low, which drastically reduces the heat transfer efficiency of the slag melt to the low thermal efficiency of this process and, consequently, the high specific consumption of fuel during the regeneration process. The aim of the invention is to increase the e efficiency of refining pig iron from sulfur, the temperature of the iron and the efficiency of the steelmaking process. The goal is achieved by the fact that according to the method of preparing a metal charge for steelmaking, including the treatment of liquid iron with slag, blown with a submersible nauseous flame torch, the slag is blown with an oxygen-oxygen torch of 1700-1900 C and mixed with iron in an amount of 50-150% mass of cast iron. In addition, cast iron is mixed with scrap in the amount of 4.4-7.2% of the mass of cast iron for every 100 ° C of its overheating. The selection of these parameters is based on the following prerequisites. First, the regeneration of desulfurizing slags by blowing them with a submerged combustion torch becomes effective when their temperature is above 1500 C. Considering that when the pig iron is displaced from the slag melt, their temperature is equalized, then the minimum heating of the iron will be determined by the temperature of 1500 C. At the same time, for the steelmaking process, considerably more heating of the pig iron is advisable. The upper level of this heating is determined by the resistance of the refractory lining and the thermal efficiency of the slag melt regeneration process. Based on the analysis of these conditions, it is advisable to take the upper level of cast iron heating equal. Secondly, in order to carry out the heat transfer process from the slag melt to the cast iron, the first must have overheating above the temperature to which the cast iron is heated, i.e. this overheating should be higher, respectively, 1500 and. With an increase in the temperature of such overheating, the thermal efficiency of slag regeneration will decrease and difficulties with the lining service (refractory or skull) will increase. With this in mind, it is advisable to produce in the process of regeneration overheating of the slag melt to 17001900 ° C. Thirdly, to heat the iron to a predetermined temperature, i.e. to 15001700 0, the slag melt should be characterized not only by the specified heating temperature, but also by a certain mass. On the basis of heat balances and their analysis, it turned out to be expedient, taking into account the selected overheating temperatures of the slag melt, to limit its mass to an amount of 50-150% by weight of cast iron. After such treatment (close mixing of iron and slag melts and their separation), the iron turns out to be cleaned from the medium to thousand fractions of a percent, regardless of its initial content, and heated to 1500-1700s. The iron thus prepared can be poured immediately. 31 into the steelmaking unit, or first mixed with the scrap and after the scrap is melted, sent to the steelmaking unit, or re-processed with fresh regenerated desulfurizing slag melt and only then fed to the steel smelting. The amount of scrap mixed with superheated iron is taken in the range of 4.4–7.2% of the mass of the latter, depending on the carbon concentration in it and its superheat temperature above the liquidus before mixing with the slag which preceded the mixing with the scrap. This method of mixing preheated scrap with the subsequent treatment of the cast iron melt with fresh slag melt can be carried out several times if necessary. After mixing with the iron melt and the subsequent; its separation from it, the desulfurizing slag melt is subjected to regeneration (purification from sulfur and heating) by blowing it with a fuel-oxygen flame from 1.0 to 1.25. Moreover, its heating begins with a temperature of 1500 starts at 1700 ° C, at which the slag has a sufficiently high liquid mobility (low viscosity), which contributes to a high dispersion and burning flame in the long run, high thermal efficiency (50-60%) of slag heating, and consequently, low specific fuel consumption. Slag regeneration can be carried out in a steel-teeming ladle equipped with fuel-oxygen tuyeres, by means of which the slag melt is subjected by blowing it with a fuel-oxygen torch and at the same time refined from sulfur and then from other undesirable impurities, and also corrected by composition and by mass (quantity) with the power of the pneumotransport system. The highest technical and economic indicators of the method can be obtained by using a continuous reactor, which is an annular chamber, which is technologically divided into three zones: the slag regeneration zone, the iron-slag mixing zone and the separation zone. The annular chambers in the regeneration zone are equipped with fuel-oxygen tuyeres, immersed7 in slag. In the mixing zone, this chamber has an opening for pouring iron into a glacier and is equipped with a pulverizing unit for crushing the iron into drops, and in the separation zone it accompanies the opening of a cast iron outlet. The bottom of the reactor is made with a slope in the direction of the hole. The arch of the annular chamber is equipped with a gas-cleaning tract. The reactor can be equipped with a pneumatic conveying system for feeding slag-forming and deoxidizing powders into the melt. In some cases, the refining and heating of the slag (its regeneration) is advisable to be carried out in cyclone or jet devices located above the ladle. In order to reduce the heat loss of the pig iron during its transportation to the steel-smelting units, it is advisable to arrange the slag preparation and treatment of the cast iron in the vicinity of these units, for example, in a mixing compartment. The method is carried out as follows. A bucket regenerating device is used to process the liquid slag. After discharging from the blast furnace, the required amount of slag is poured into a special dead-drain bucket, its volume is filled by 50-75%. If this slag requires a chemical composition adjustment, the necessary additives, such as lime, are set in the ladle before draining fresh slag there, or in powder form are introduced into the slag melt with flare jets during slag processing. The slag poured into the slag poured into the refining bucket is dipped into the purge tuyeres, which are used to purge the gas-oxygen torch, first with an oxygen consumption coefficient (about) close to 1.1, and as the slag is heated, it is increased to 1.25. After reaching the desired degree of desulfurization of the slag and, if necessary, continue its heating, it is transferred to purging it with a torch with ot | 1.0 With the increased content of iron or manganese oxides in the slag, a reducing (deoxidizing) period is followed by an oxidizing one. During this period, the slag is flushed with a flame of incomplete combustion and powder deoxidizing agents (coke, calcium carbide, ferrosilicon) are blown into the slag simultaneously with the torch. After the necessary refining of slag and its overheating is completed, the ladle is freed from tuyeres, and the finished slag is drained from it into a mixing vessel, for example, another larger-type ladle with a different hole in the bottom, in which the pig iron is simultaneously drained. Drainage of slag and cast iron into the mixing vessel is carried out from a height ensuring close mixing (emulsification), and which is established experimentally for these specific conditions of such treatment.

After this treatment and settling, the duration of which is determined experimentally, the cast iron is poured into the cast iron ladle with a small amount of slag through the casting hole to reduce the heat loss of the iron, and the slag remaining in the mixing vessel is returned to the refining ladle where it is regenerated

When used to treat cast iron slags of the synthetic type, for example, lime-alumina, they are initially prepared in a refining ladle by gradually directing it into a small bath formed from a liquid blast furnace slag and constitute, for example, 5-10% of the weight of the slag being prepared. Otherwise, the preparation and regeneration in its methods remains the same as when using blast-furnace slags. If there are slag-smelting electric furnaces at the plant, initially slag can be prepared in these units. Taking into account the scarcity and high cost of alumina, when casting the iron from the mixing ladle, do not allow the iron to be covered with lime-alumina slag. Instead, on the surface of the cast iron in the cast iron ladle pour or fall asleep the corresponding amount of the usual blast furnace. The implementation of the proposed method in the reactor of non-rigorous action begins with the preparatory operations for the preparation of synthetic. desulfurizing slag, which are characteristic of the methods of preparing such slag on the basis of liquid blast-furnace or lime-alumina in a ladle-type device. After cooking liquid

slag melt

The eio is blown in the regeneration zone with the help of oxygen-oxygen tuyeres with a full combustion flame to remove and heat sulfur from the slag. If necessary, adjust the composition of the slag, including by deoxidation. Under the action of the jets of the fuel-oxygen torch due to the special arrangement of the nozzles in the tuyeres, the slag continuously moves along the annular chamber passing all the zones sequentially. Cast iron is poured into the mixing zone through the pouring hole and the pulaization unit. The small droplets of cast iron in the separation zone, precipitated through the slag melt on the sub, are cleaned of sulfur and heated. Next, the slag reaches regeneration and the process cycle for the slag is repeated. Cleared of sulfur and heated by a pig iron continuously flows from the reactor through the outlet to the ladle.

When converting a blast furnace to work with low basicity slags, they increased the furnace productivity by 10-12% and reduced coke consumption by 7-8%, but at the same time the sulfur content sharply increased in the produced iron: from 0.04 to 0.35%.

At the same time, in the converter shop it was necessary to increase the productivity of converters by 10% and the metal yield by 1.5-2.0% due to a decrease in the concentration of sulfur in the iron to 0.01%, and also to increase scrap processing by 8-10% from the weight of the metal dumping device due to overheating of the pig iron coming to the converters e 1250 to 1500 ° С.

The above requirements for cast iron entering the converter shop were met by cast iron arriving after the treatment with superheated desulfurizing slag. Initially, the head was prepared from fresh domain, having a basicity of 1.0 and a temperature of 1350 C, which contained about 2.0% sulfur. By its oxidative purging in the refining bucket with a fuel-oxygen torch with a coefficient of oxygen consumption (oi) from 1.0 to 1.25, sulfur was removed from the slag d 0.05%. At the same time, during this period, an appropriate amount of lime was added at the rate of increasing the basicity to 1.2, the daini composition of the slag was characterized by an equilibrium distribution coefficient equal to

80. Therefore, such a slag, when emulsifying with a cast iron, provided its necessary desulfurization (reduction of sulfur from 0.25 to 0.01%) if its amount relative to cast iron by mass was not less than 36%. However, this amount of slag to ensure heating the cast iron when they were mixed into given ones required that the slag be overheated before. It was advisable to limit the temperature of its overheating to 1750 C. Therefore, in order to maintain a balance in its heat content, the slag mass was increased to 75% with respect to cast iron, and taking into account compensation of heat losses to 80%.

The finished slag was poured simultaneously with the cast iron into a separate ladle with a height: about 4 m and after settling, the cast iron was released into the cast iron carrier through the bottom hole, and the slag with a temperature of about 1500 C was returned to the refining ladle for regeneration, where the appropriate amount of fresh blast furnace slag was added and lime to compensate for mechanical losses of 5%. This slag was first blown with an oxidative fuel-oxygen torch with the same mode as in the initial preparation of slag, and then with a reducing torch with a cd of 0.5 with simultaneous feed into the slag together with the blown ground coke (coal) in an amount of 0.5% to the weight of slag to reduce the concentration of iron oxide and manganese oxide in it. After that, the slag was again sent to the processing of cast iron, then it was again subjected to regeneration, repeating this cycle many times.

Natural gas was used as fuel for heating slag, and its consumption for one cycle of slag regeneration was W m per 1 ton of treated iron. The consumption of oxygen, respectively, was 22.5 m. The coefficient of useful use

0 crowd was close to 0.64.

Thus, the increase in the mass of slag (-13 times) and its desulphurisation capacity due to its high temperature, and therefore,

5 and liquid mobility increased the degree of desulfurization of cast iron from 50-70 to 98% (sulfur in the iron decreased to 0.004%), and the amount of sulfur removed from its sulfur from 0.015-0.035 to-0.246%, i.e. at

0 7-16 times.

A multiple increase in the amount of sulfur removed from the cast iron made it possible to transfer the blast furnace to work with lower slag basicity.

5 and with the release of sulfur iron,

containing 0.25% sulfur instead of the usual, for example, 0.040%, which made it possible to increase the productivity of the blast furnace by about 10-12% and at the same time reduce the coke consumption by about 7-8%.

I

Heating the cast iron did not allow for increasing scrap recycling by about 10% when working with this iron in a converter, and when working with the same iron in an open-hearth furnace to increase its productivity by an average of 25%,

Claims (2)

1. METHOD FOR PREPARING A METAL CHARGE FOR MELTING STEEL, including treating liquid cast iron with slag blown by a submerged fuel-oxygen combustion torch, characterized in that, in order to increase the efficiency of refining cast iron from sulfur, the temperature of cast iron and the economy of steel-smelting, the process is smelting torch up to 1700-1900 ° C and mix it with cast iron in an amount of 50-150% of the mass of cast iron. 2. The method of pop. ^ distinguishing with scrap in cast iron by the fact that cast iron is mixed in an amount of 4.4-7.2% of the mass ’’ every 100 C of its overheating. to black use steel.