SU1638174A1 - Method of preheating of scrap in basic oxygen furnace - Google Patents

Description

one

(21) 4257232/02

(22) 05.06.37

(46) 03/30/91. Bul tf 12

(71) Karaganda Metall. Combine

(72) V.I.Bogomov, V.P.Tsymbal, I.I. Esipenko, B.A.Burdonov, V.I.German and V.S.Sherba

(53) 669.134.244 (033.8)

(56) USSR Copyright Certificate No. 440613, cl. C 21 C 5/23, 1971.

USSR Author's Certificate No. 963075, cl. C 21 C 5/23, 1932. Steel, 1936, N 10, p. 9-10.

(54) METHOD FOR PRELIMINARY HEATING OF SCRAP IN THE CONVERTER

(57) The invention relates to ferrous metallurgy, more specifically to the production of steel in oxygen converters, and can be used to preheat scrap in the converter. The purpose of the invention is to reduce the consumption of iron and the cost of steel by increasing the consumption of scrap by increasing the efficiency of its heating. According to the invention, the maximum dispersion of solid fuel in the scrap volume and the effect of volumetric heating without melting and evaporation of the charge are provided. Scrap heating is carried out in an amount of 40-75% of the total smelting expenditure during cyclic reciprocating movement of the oxygen tuyere with its holding in the lower position. Solid fuel is introduced in equal portions of 20-25% of the total consumption at the moment of movement of the tuyere up from the bottom position. The shutter speed in the lower position is 70-130 s. The invention allows to reduce the cost of steel by reducing the consumption of pig iron and increasing the proportion of heated scrap in the metal charge. 1 ill., 1 tab.

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The invention relates to ferrous metallurgy, more specifically to the production of steel in oxygen converters, and can be used to preheat scrap in the converter.

The purpose of the invention is to reduce the consumption of iron and the cost of steel by increasing the consumption of scrap by increasing the efficiency of its heating.

The drawing shows a graph of the heating of scrap.

According to the proposed method, scrap is loaded into the converter in the amount of 40-75% of the total consumption per

melting, heating is performed with cyclic reciprocating movement of the oxygen tuyere with a minute oxygen consumption of 5–20 nm / ton of scrap, while solid fuel is introduced at the moment the tuyere moves up from the lower position at the scrap level to the top until the throat is cut. 20-25% of the total consumption with an interval of 70-130 s. To accelerate the ignition of coal, the first batch of solid fuel is introduced in a mixture with aluminum-containing materials.

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In large-size converters with a capacity of up to 300-400 tons with an existing scrap consumption of 23-27% of the weight of the metal charge, the scrap weight is 100-120 tons or more, and with scrap heating this value increases by 10-20 tons. scrap even at very high thermal power of a gas-oxygen or fuel-oxygen torch supplied from above is impossible. The method also takes into account the fact that in the converter shops the scrap filling is made, as a rule, by 1-4 scoops, and less frequently 5-10.

Practical experience shows that when scrap is heated by oxygen from above in an amount of less than 40% of the total smelting expenditure, the heat supplied is not efficiently used, some of the scrap is melted and the heating of large pieces is delayed by the presence of a liquid iron oxide film on their surface. The% - scrap does not heat over the entire height, since the height of the metal charge layer is large enough, this leads to a lengthening of the heating period and to an increase in the total duration of smelting and a decrease in the manufacturer

converter.

The raising of the tuyere with simultaneous supply of oxygen during the period of input of solid fuel from above contributes to its dispersion (dispersion and scattering) by its stream of oxygen over the surface and in the scrap volume.

After lowering the tuyere to the lowest position and holding it for 70-130 s, a portion of the fuel is completely burned in the scrap volume. During this period, all coal burns completely. In the next raising of the tuyere, the next portion of solid fuel is introduced, and the cycle is repeated.

3 As a solid carbon-containing fuel for preheating scrap according to the proposed method, coal grade AC with a calorific value of 6,230 kka / kg is used. The heat content of the liquid iron that is excluded from the process (replaced by metal scrap) is compensated by the heat from the combustion of the solid fuel with oxygen.

In a heavy-duty converter containing 100-150 tons of scrap with a low bulk density (0.6 - 0.7 tons / m9) in the filling, it is not possible in a number of cases.

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place the entire scrap in the converter when loading the entire volume of the converter to the neck. In this case, a part of the scrap is introduced into the converter, and after it is heated to 600-300 ° C, a lightweight part of it precipitates (the scrap is settled) and the volume is freed up to load the remaining amount of the charge.

Calculations show that with the consumption of solid fuel in the amount of 16-20 kg / ton of steel from its combustion (taking into account the fuel utilization factor - KIT), heat is generated sufficient to compensate for the heat content of 1.0 ton of liquid iron and to heat 1.0 ton of scrap up to 600-800 C. The method of introducing solid fuels for heating scrap is of paramount importance. The introduction of 1.0 tons of coal into the converter into the filling allows for an additional 2.3-2.8 tons of scrap metal to be processed, 2.3 to 3.6 tons of scrap for heating before the pig iron is loaded, 3.8 for heating in portions during heating. -4,4 tons of scrap. According to the proposed method, the supply of solid fuel to scrap heating is carried out in the converter as dispersed as possible during the period of raising the tuyere and with oxygen consumption of 5-20 nm / min per 1 ton of scrap. The effect is achieved by burning the fuel within the volume of scrap between the pieces. Oxygen supply less than 5 nm / min is insufficient for burning one-time input 20-25% of fuel from the total consumption for heating, and when supplying more than 20 nm / min per ton of scrap a significant part of oxygen is lost with gases and does not participate in fuel combustion. The fuel is supplied in the process only when the lance moves upwards in order to prevent local overheating of even the lightweight part of the scrap.

Entering the fuel in even portions at intervals of 70-130 seconds allows the previous portion to be completely burned, while increasing the thermal efficiency of the solid fuel.

At intervals of less than 70 seconds, an incomplete combustion of a portion of the fuel takes place, since its introduction is accelerated, and at intervals of more than 130 seconds, oxygen is consumed not only for burning coal, but also for oxidation of iron (partially); it is melted, and the total period is extended

heating scrap. It has been established that with a one-time fuel input of less than 20% of the total consumption for heating scrap, the number of cycles increases and the total heating time increases, although this affects the degree of heat absorption of fuel favorably. When the amount of fuel is more than 25% of the total consumption for heating, there is a local overheating of scrap and its melting, uneven heating of scrap.

Example. According to the proposed method, 56 tons of scrap (2 scoops) were loaded into a converter with a capacity of 365 tons - 46% of the total consumption for smelting (a total of 120 tons of scrap and 235 tons of pig iron were introduced for smelting versus 110 and 245 tons, respectively, according to known technology). For heating scrap, grade AC coal was used in the amount of 5.6 tons for smelting (13.0 kg / ton of steel). The number of coal feed cycles was taken equal to 4, 1.4 tons each (25% of the total consumption for smelting). The tuyere was set at the level of scrap loaded into the converter. The heating process was started with simultaneous feeding from above of 1.4 tons of coal, raising the tuyere to the throat level with the oxygen consumption starting at 670 Nm3 / min (12 nm / min per 1 ton of scrap). The torch on the vils on the neck after 40 s from the beginning of the lifting of the tuyere. In the upper position, the lance was kept for 2-3 s and lowered to the level of scrap. In the lower extreme position, the lance was aged for 110 s. After that, the full cycle was repeated three times. During the entire period of scrap heating (8.2 min), the oxygen consumption was constant - 670 nm / / min. The scrap temperature according to the interferometer readings was 812 ° С under the tuyere, and 384 ° C. near the converter walls.

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Examples of the implementation of the proposed and known methods are presented in the table.

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As a result of the use of the booster, the scrap heating efficiency is increased by increasing the thermal efficiency of the fuel, reducing the oxygen content in the exhaust gases during the heating period, increasing the uniform heating of the scrap in its volume and reducing the overheating with the elimination of its melting and evaporation of the charge.

The application of the proposed method allows to reduce the cost of steel produced by increasing the share of scrap in the metal charge and reducing the consumption of pig iron.

Claims (1)

Invention Formula The method of preheating scrap in the converter, including filling scrap, solid fuel additive, burning it in jets of oxygen supplied by a tuyere from the top with a minute consumption of 5-20 Nm3 / t of heated scrap, characterized in that in order to reduce the consumption of iron and the cost of steel by increasing scrap consumption by increasing its heating efficiency, scrap heating is carried out in an amount of 40–75 vol.% of the total smelting cost during cyclic recurrent displacement of an oxygen tuyere with an exposure of the tuyere in the lower half in the range of 70-130 s, at that, solid fuel is introduced in equal portions of 20-25% of the total consumption at the moment of tuyere movement up from the lower position at the scrap level to the upper one up to the throat cut. 22 25 24 25 120 90 120 iao 9,014,7 7,013,2 9,217,6 10,215,6 90 20 130 12.0 16,436.0 55 sixteen 100 55 55 55 55 20 23 25 32 120 120 130 110 70 20 p5 4.0 16.2 Zonal no- introduced coal lance on Nag-during heating / 5-roaring 22 45 × 7.0 12.5 , 0 , 0, 5 5.8 6.0 9.0 7.8 13.5 10.0 9.2 6.0 15.9 746 759 772 664 624 805 738 801 705 632 5Vy scrap - melting, the presence of liquid so composing Normal heating of scrap The same - and Scrap is not heated, the smelting cycle is extended, black scrapers are on the converter walls. Uneven heating of scrap, reduced converter performance, low average scrap temperature. The warm-up time increases dramatically. Smelting cycle increases. Normal heating of scrap x Same Local heating scrap, oplavlent. scrap, uneven 1 heat, low heating temperature Incomplete cropitme coal, oxygen is lost in the gaseous phase with unburned fuel Normal heating of scrap Same II The melting of the beam, the lengthening of the melting cycle,. uneven heating Scrap is heated unevenly - white at the center of the converter and black at the walls, the presence of a liquid component , 5 9.5 583 Also Scrap is heated to form a liquid 4 Also At the converter walls there is black scrap, in the center liquid scrap was made up of usha, black scrap At the converter walls