RU2251575C1 - Method for creating protection lining slag in shaft of blast furnace - Google Patents

Abstract

FIELD: ferrous metallurgy, particularly cast iron production in blast furnaces.

SUBSTANCE: method comprises steps of cyclically loading charge materials such as lining slag generating material; introducing material into peripheral zone of furnace; monitoring thermal loads of coolers of shaft. Lining slag generating material consists mixture of iron ore and part of agglomerate of its total quantity in batch or dose at percentage relation: iron ore -agglomerate (5 - 15):(95 - 85) for mass of mixture providing quantity of primary slag melt 20 -25% including no more than 15% of ferrous oxide. When thermal load of coolers of shaft of blast furnace achieves admissible value or exceeds it, mixture is introduced into each batch or dose of cycle respectively at ladle or conveyer charging.

EFFECT: increased time period between restoration works of lining of shaft of blast furnace, increased useful life period of shaft.

3 cl, 3 tbl

Description

The invention relates to the field of ferrous metallurgy, in particular to the production of pig iron in blast furnaces.

There is a known method of blast-furnace smelting [1], in which titanium-containing components — slag, an agglomerate of a special composition — are introduced into the charge. The method allows to partially restore the lining in the furnace of a blast furnace, where the temperature develops up to 1600-1700 ° C and titanium-containing components pass through the stage of melting and reduction with the formation of refractory carbides and carbonitrides. However, these materials remain “dry” on the horizons of the mine and not only do not contribute to skull formation in these zones, but also act as abrasive material when they are loaded into the peripheral zone of the furnace.

Closest to the claimed technological essence is a method of creating a protective skull in a blast furnace [2], in which the skull-forming additive is represented by slag-forming crushed stone - a product of blast furnace slag processing, which is obtained by melting titanium-magnetite iron ore materials in a blast furnace. The garnisage-forming additive contains titanium carbonitrides, which are refractory independent inclusions in the matrix of crushed stone pieces and are not involved in the formation of melts at the mine horizons. The polyelement composition of the additive, when heated and restored to its “stratification” into refractory titanium and calcium magnesium-containing components with the formation of the last primary slag melts with increased “aggressiveness”, leads to the residual fireclay type of broadband lining, penetrate into it, causing a gradual “degeneration” and subsequent destruction of the refractory material along the height of the shaft of the blast furnace. In addition, the frequency of introduction of the skull-forming additive leads to the fact that the layer of the skull resulting from its introduction can be erased by subsequent portions of materials containing no additive.

In the proposed method for creating a protective skull in the mine of a blast furnace, including cyclic loading of charge materials, including skull-forming material, introducing it into the peripheral zone of the furnace, controlling thermal loads on the mine refrigerators, a mixture of iron ore and parts is formed as a skull-forming material during loading agglomerate of its total amount in the feed or portion taken in the percentage of ore: agglomerate (5-15) :( 95-85) in relation to the mass of the mixture, providing primary sludge of molten melt from it in an amount of 20-25% with a share of iron oxide of not more than 15%, while at the time the heat loads on the refrigerators of the blast furnace mine approach the permissible value established by the project or exceed it, the mixture is introduced into each feed or portion of the loading cycle.

During skip loading of a blast furnace, iron ore is fed to the first skip for sinter, and during conveyor - to the head of the portion together with sinter.

A positive result achieved by the proposed method lies in the possibility of “healing” the lining of the mine shaft of the blast furnace (technical result) and prolonging the campaign of the blast furnace for a certain period beyond its standard service, saving investments and the interest rate on them by the value of this rate and extending the campaign (economic result).

The essence of the method is as follows.

The sinter plant of the metallurgical plant supplies iron ore raw materials to a block of blast furnaces that differ in terms of life and condition of the lining. The production of a special composition of agglomerate for directed skull formation on one of the furnaces will cause a change in charge-technological conditions on all other furnaces and adversely affect the stability of their operation. At the same time, the housekeepers cannot influence the composition of the pellets, because pelletizing factories are not part of metallurgical plants and are suppliers of a large number of consumers.

Therefore, in order to create a blast furnace charge with a given melting temperature for scaling along the shaft height of an individual furnace without changing the composition of the pellets and sinter, it is necessary to mix the latter with raw iron ore in a certain ratio, providing the indicated temperature softening-melting parameters with the formation of an increased amount of a primary low-aggressive FeO content melt. In contact with the residual lining, such a melt forms a skull on a certain mine horizon, without penetrating into the lining and without destroying it, which is determined by the content of iron oxide in the primary melt from iron ore materials.

Since it is impossible to carry out direct measurements in a blast furnace, the temperature ranges of softening and melting of the reduced iron ore materials and the primary slag formation process were modeled according to the procedure [3].

The interaction of the melt with the lining was determined by the following method. Preliminarily reduced materials or their mixture were placed and heated to 1250-1400 ° C between nickels from fireclay grade ШПД with a diameter of 48 mm and a thickness of 12 mm. The depth of penetration of the melt into the lining was used to judge the aggressiveness of the melt.

The beginning of the appearance of liquid phases or “test formation” and the interval of their melting are model reflected in the interval of 45% shrinkage of the layer and the beginning of melt filtration through the coke nozzle.

The chemical composition of the materials used and the test results are presented in table. 1.

The test results show a high “aggressiveness” of the melt from the pellets and increased - at a high proportion in the mixture with the agglomerate due to the high content of FeO in the primary melt (experiments No. 2, 5, 6 and 7). The melt with the participation of slag crushed stone is also significantly introduced into the refractory mass due to the chemical interaction of chamotte and the main melt (experiments No. 4 and 11). In both cases, the “rebirth” of the refractory occurs and its subsequent destruction.

Table 1 The chemical composition of the materials, the characteristics of softening-melting, slag formation and the depth of penetration of the melt. No. of experiments Material Content% T ₄₅ T _nf FeO _psh M _psh GP Fe FeO CaO SiO ₂ MgO Al ₂ O ₃ TiO ₂ 1 Agglomerate (A) 58.80 13.00 7.66 5.10 2.49 0.95 0.40 1370 1430 11.0 6.8 1-2 2 Pellets (O) 63,20 1,50 3.69 4.99 0.26 0.33 - 1260 1350 36,2 28.1 8-12 3 Ore (P) 44.40 6.20 3.07 27,20 0.36 0.42 - 1400 1560 27.0 6.0 0-1 4 Crushed stone slag (W) 3.8 1,0 30.1 29.5 11.5 14.3 9.6 1300 1345 4.9 19.0 4-6 Mixtures: 5 63% A 60,43 8.75 6.19 5.06 1,66 0.72 0.24 1270 1395 14.0 15,5 3-5 37% O 6 70% A 60.12 9.55 6.47 5.07 1.82 0.76 0.25 1275 1395 11.7 15.6 3-5 30% O 7 34% A 61.70 5.41 5.04 5.03 1,02 0.54 0.14 1250 1380 25.0 15.1 6-8 66% O 8 85% A 56.64 11.98 6.97 8.42 2.17 0.87 0.33 1270 1360 fifteen 25.1 2-3 15% P nine 90% A 57.36 12.32 7.20 7.31 2.28 0.90 0.35 1285 1395 7.4 23.5 1-2 10% P 10 95% A 58.10 12.55 7.40 6.45 2.40 0.92 0.38 1295 1400 6.4 20,2 1-2 5% P eleven 66% A 56.73 9.06 7.90 6.53 2.41 1,58 0.84 1285 1380 11.3 19.5 4-5 28% O 6% W T ₄₅ - temperature of 45 percent shrinkage of the layer, ° C; T _nf — temperature of the beginning of melt filtration through a coke layer, ° С; FeO _nu - iron oxide content in the primary slag,%; M _PSH - the mass of primary slag in relation to the mass of the sample,%; GP - depth of penetration of the melt into the lining material, mm

Pure agglomerate does not create an “aggressive” melt, however, the amount of the latter and high softening-melting temperatures (experiment No. 1) do not allow the formation of a skull on the horizons of the furnace shaft.

Optimal results were achieved in experiments Nos. 8, 9 and 10, in which a mixture of iron ore and agglomerate, taken in the percentage ratio in the mixture (5-15): (95-85), was formed as a skull-forming material.

In industrial conditions, the method of creating a skull is implemented as follows.

In normal mode, smelting is carried out on a 2002 m ³ blast furnace equipped with skip loading with a conical filling apparatus. The loading cycle consists of five feeds with two skips in each. The loading system is shown in table. 2.

table 2 Normal blast furnace loading system Feed Charge Consumption, t First skip Second skip Agglomerate Ore Converter slag Pellets Agglomerate 1 17 2 0 12 7 2 16.5 0 2,5 12 7 3 19 0 0 12 7 4 19 0 0 12 7 5 19 0 0 12 7 6 17 2 0 12 7 7 16.5 0 2,5 12 7 8 19 0 0 12 7 nine 19 0 0 12 7 10 19 0 0 12 7

With the design norm of the heat load in the furnace shaft for 2-3 rows of plate refrigerators in the zone 583200 kcal / hour, the furnace operates with a heat load of 550800 kcal / hour.

At a certain period, an increase in thermal loads begins at a given mine horizon and this phenomenon assumes a continuous character, which indicates the sliding of the skull and, possibly, partial destruction of the lining on this horizon.

The introduction within three days of slag crushed stone containing titanium carbonitrides in an amount of 6% by weight of the iron ore part of the charge was accompanied by a decrease in the water temperature difference in the hearth refrigerators, which indicated an increase in the skull in this place, but did not stop the trend of increasing thermal load on the mine refrigerators.

For directed creation of a skull on this horizon of the mine, the loading system is changed according to the proposed method, introducing a mixture of ore and sinter in a ratio of 5.6%: 94.4% is carried out at each feed of the loading cycle (Table 3). For mixing with the agglomerate and getting the mixture to the periphery, the ore is fed into the first skip to the agglomerate.

Table 3 Blast furnace loading system with the creation of a skull in the mine Feed Charge Consumption, t First skip Second skip Agglomerate Ore Converter slag Pellets Agglomerate 1 eighteen 1 0 12 7 2 15,5 1 2,5 12 7 3 eighteen 1 0 12 7 4 eighteen 1 0 12 7 5 eighteen 1 0 12 7 6 eighteen 1 0 12 7 7 15,5 1 2,5 12 7 8 eighteen 1 0 12 7 nine eighteen 1 0 12 7 10 eighteen 1 0 12 7

Since the blast furnace is an inertial unit, the thermal load on the mine refrigerators continues to grow for some time and reaches 610,500 kcal / h.

A day after the installation of the proposed loading system, the thermal loads stabilize and begin to decline, reaching the norm in 2 days. The loading system is put into continuous operation.

On blast furnaces equipped with a conveyor charge supply system and a gas supply unit, the formation of a skull-forming mixture is carried out by supplying iron ore to or under an agglomerate (depending on the position of the bunkers on the charge supply) in a predetermined ratio in the head of a portion on a conveyor.

Thus, the use of the proposed method of creating a protective skull allows you to increase the period between overhauls of a mine of a blast furnace of the second category for a certain period of time and generally extend the campaign of a blast furnace.

Used sources

1. The method of blast furnace smelting. Auth. testimonial. USSR No. 1401046, C 21 V 5/00. Publ. 06/07/88. Bull. No. 21.

2. A method of creating a protective skull in a blast furnace. Pat. Russian Federation No. 2179583 C 21 V 5/00. Publ. 02/20/2002. Bull. No. 5.

3. N.A. Gladkov, A.S. Nesterov. Processes in a layer of iron ore materials when it is heated // Bulletin of the USSR Academy of Sciences. Metals 1987, No. 3, pp. 9-11.

Claims (3)

1. A method of creating a protective skull in a mine of a blast furnace, including cyclic loading of charge materials, including skull-forming material, introducing it into the peripheral zone of the furnace, controlling thermal loads on the mine refrigerators, characterized in that a mixture is formed as a skull-forming material during loading iron ore and part of the agglomerate of its total amount in the feed or portion taken in the percentage ratio of ore: agglomerate (5 ÷ 15) :( 95 ÷ 85) in relation to the mass of the mixture, providing primary of slag melt from it in an amount of 20 ÷ 25% with an iron oxide fraction of not more than 15%, while at the time the heat loads on the refrigerators of the blast furnace mine approach the permissible value established by the project or exceed it, the mixture is introduced into each feed or portion of the loading cycle . 2. The method according to claim 1, characterized in that when skip loading a blast furnace, iron ore is fed into the first skip for sinter. 3. The method according to claim 1, characterized in that during conveyor loading of a blast furnace, iron ore is fed to the head of the portion together with the sinter.