RU2609885C1 - Extrusion briquette for blast furnace process - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to ferrous metallurgy, namely, obtainment extrusion briquette for blast furnace process. Extrusion briquette obtained by stiff vacuum extrusion consists of metallurgy scales, carbon-containing material, bentonite and cement, and contains, wt %: FeO < 40; Fe₂O₃ > 20; MgO 0.01-2.5; MnO 0.01-9.0; Cr₂O₃ 0.01-1.5; C 0.1-75.0; S 0.01-0.5; SiO₂ 0.1-15.0; TiO₂ 0.01-0.1; CaO 0.1-7.0; Al₂O₃ 0.01-1.5, impurities < 2, where content of Fe_total comprises 10.0-58.0. Compression strength is at least 5.0 MPa, specific density is at least 2.8 kg/dm³, open porosity comprises at least 10 %, and softening start temperature is at least 1200 °C.

EFFECT: possible obtainment of briquettes with high physical and chemical properties that allow for high performance of cast iron and optimize cast iron production process in a blast furnace due to early formation of carbon oxides and faster reduction of iron from oxides.

2 cl, 1 dwg, 3 tbl, 2 ex

Description

The invention relates to the field of ferrous metallurgy, and in particular to the production of an extrusion briquette containing metallurgical waste, in particular metallurgical scale, intended for the production of pig iron in a blast furnace.

The prior art briquette for blast furnace production, in particular, disclosed in patent RU 2241760, class. C22B 1/243, publ. 12/10/2004. The known briquette is obtained by vibropressing from a charge, including carbon-containing materials, iron-containing materials, fluxing additives and mineral binder, the size of the materials included in the charge does not exceed 10 mm The disadvantage of this known technical solution is that the known briquette does not provide for the use of metallurgical waste in its composition, which limits the possibility of their disposal with widespread use of briquettes. In addition, the size of the briquettes significantly exceeds the optimal sizes of pieces of charge materials of blast furnace smelting, which complicates their loading and reduces the efficiency of use in a blast furnace. In addition, the technology of vibrocompression, according to which the briquette is produced in a known technical solution, is discrete according to the operating principle, has limited performance, requires increased consumption of cement and heat for curing the briquettes.

Also known are extrusion briquettes for blast-furnace smelting, made by rigid vacuum extrusion of iron-containing material, carbon-containing material in the form of coke breeze, Portland cement and bentonite (Kurunov I.F. et al. Metallurgical properties of bracks., Metallurg, No. 6, 2012, ss. 44-48), as well as briquettes from a mixture of mill scale, cement and fluxing additives (Bizhanov AM et al. Study of the mechanical strength of BREKS. Part 2, Metallurg, No. 10, 2012, pp. 36-40).

The closest analogue of the invention is an extrusion briquette for blast furnace production, disclosed in patent RU 2506326 C1, cl. C22B 1/243, publ. 02/10/2014. The well-known briquette is made by rigid vacuum extrusion from a mixture of iron-containing materials (including mill scale), carbon-containing material, mineral binder (6-7% Portland cement) and fluxing additives (0.5-1% bentonite). The density of the obtained briquettes was 2.0-2.2 g / cm ³ , the crushing strength after aging for 48 hours was 5.3 MPa. In the process of blast-furnace smelting, the known briquette remains in shape until it comes to a temperature zone of 1100-1250 ° C, where it softens and melts. The disadvantages of the known briquette are insufficiently optimal physical properties and chemical composition and, accordingly, qualitative characteristics of the resulting cast iron.

The objective of the invention is the manufacture of an extrusion briquette with predetermined chemical characteristics, allowing it to be used as a component of a charge in a blast furnace to partially replace iron-containing raw materials and blast furnace coke.

The technical result of the invention is to obtain briquettes with high physical and chemical properties, uniform quality, which provide high-quality characteristics of cast iron and optimization of the production of cast iron in a blast furnace.

To achieve the specified technical result, the claimed briquette obtained by hard vacuum extrusion from mill scale, carbon-containing material (8-75%), bentonite (1-2%) and cement (5%) contains, wt. %:

FeO <40 Fe ₂ O ₃ > 20 MgO 0.01-2.5 MnO 0.01-9.0 Cr ₂ O ₃ 0.01-1.5 FROM 0.1-75.0 SiO ₂ 0.1-15.0 TiO ₂ 0.01-0.1 Cao 0.1-7.0 Al ₂ O ₃ 0.01-1.5 impurities <2

the content of Fe _total is 10.0-58.0, the compressive strength is at least 5.0 MPa, the specific gravity is at least 2.8 kg / dm ³ , the open porosity is at least 10%, and the temperature of the onset of softening - not less than 1200 ° C.

Extrusion briquette is obtained by the method of hard vacuum extrusion using mill scale of a separate metallurgical production with the corresponding chemical composition, which provides a briquette of a given composition. In the particular case, it is possible to prepare the mixture using scale of various industries with the appropriate chemical composition, ensuring the achievement of a given chemical composition.

These elements in oxide forms provide high quality characteristics of cast iron and optimize the process of production of cast iron in a blast furnace due to the early formation of carbon oxides and reduce the recovery time of iron from oxides.

Iron in oxide forms is the raw material for reduction, providing an increase in suitable for the production of cast iron. The use of briquettes with a content of Fe above 58% _total (including the content of FeO> 40%) iron complicates the recovery process.

Carbon in the carbon-containing component plays the role of a fuel reduction element, reducing the consumption of coke.

The content of CaO, MgO, Al ₂ O ₃ , SiO ₂ in the indicated ranges in the briquette promotes the fluxing of coke ash and the formation of homogeneous, completely molten, liquid-moving slags, which ensure desulfurization of cast iron and facilitate the release of slag from the furnace.

The manganese contained in the briquette in oxide form in an amount of 0.01–9.0% is restored and serves as an alloying element in the production of manganese cast irons. Manganese inhibits the release of graphite, promotes the grinding of perlite and bleaching cast iron, interacting with sulfur, neutralizes its harmful effect.

The silicon content of the briquette in the oxide form in the amount of 0.1-15.0% is restored and serves as an alloying element in the production of silicon cast irons. Silicon increases fluidity, reduces shrinkage, alloys ferrite, while its increased content reduces ductility, increases hardness, and reduces tensile strength.

The chromium contained in the briquette in oxide form in an amount of 0.01-1.5% is restored and serves as an alloying element that increases the heat resistance, corrosion resistance and wear resistance of the alloy.

Contained in the composition of the briquette titanium in oxide form in an amount of 0.01-0.1% is restored and serves as an alloying element that neutralizes nitrogen in cast iron.

The briquette also contains impurities, the total content of which does not exceed 2 wt.%.

To obtain an extrusion briquette, scale of -3 mm fraction of a separate metallurgical production is used, or a mixture is prepared using scale of various industries to achieve the required chemical composition. Dross is mixed with carbon-containing material 8-75% and with 1-2% bentonite, additional mixing is carried out in the mixing screw with the simultaneous addition of water to obtain a homogenized mixture, the mixture is aged for 8 to 24 hours, the mixture is mixed in a twin-roll mixer with the addition of 5% cement as a binder and water to achieve a mixture moisture of 12-15%, feeding the extruder into the vacuum chamber with preliminary compaction of the mixture in the extruder dosing device and passing it through an extruder made with a fixed front part Tew main axis of the extrusion screw.

The technological process for producing briquettes by the method of hard vacuum extrusion in the presence of a binder is given below with reference to the attached scheme 1.

Schema Positions:

1 - the site of the reception of raw materials;

2 - Separation site;

3 - Raw materials warehouse after separation;

4 - Bunker No. 1;

5 - Bunker No. 2 carbon-containing raw materials (coke, coal fines);

6 - Bunker No. 3 bentonite;

7 - Conveyor No. 1;

8 - Mixer;

9 - Conveyor No. 2;

10 - Warehouse for sludge prepared mixture;

11 - Receiving hopper for the prepared mixture;

12 - Silo No. 1 cumulative;

13 - Silo No. 2 cumulative (spare);

14 - Silo No. 3;

15 - Conveyor No. 3;

16 - Two-roll mixer;

17 - extruder dispenser;

18 - extruder;

19 - Conveyor No. 4;

20 - Land for finished briquettes (chest);

21 - Warehouse for finished products.

Separation plot

At this site, preliminary separation of the starting materials by particle size distribution is performed to obtain acceptable particle sizes. The quality of raw materials arriving at the site in the form of mill scale with a moisture content of 0.3-10% is checked in a chemical laboratory.

Scale is divided into 3 fractions at the McCloskej international 130 installation. The feedstock is fed to the McCloskej international 130 installation with a front-end loader. As a result of separation, the following fractions are distinguished: fraction +10 mm; fraction -10 + 3 mm; fraction -3 mm.

The + 10 mm and -10 + 3 mm fractions are not involved in the technological process, are moved by the front-end loader in GEL and are subject to sale to consumers. To implement the method, a scale of -3 mm fraction is used, which is to be further processed on a separator to obtain satisfactory quality of the prepared materials, removal of small metal inclusions in the form of needle shavings, which are unacceptable for the technological process of processing scale.

Charge preparation section

At this site, dry mixing of the feedstock and plasticization is performed to obtain a homogeneous mixture of scale, carbon-containing feedstock and bentonite and the sludge of the mixture to achieve a state of swelling of bentonite and increase the elasticity of the prepared mixture.

After separation, the raw material enters the charge preparation section.

Dross of -3 mm fraction by a front-end loader is fed into hopper No. 1, from which through a screw feeder to conveyor No. 1. Simultaneously with the scale, carbon-containing raw materials are fed from hopper No. 2 and bentonite from hopper No. 3 to conveyor No. 1 through a screw feeder. At the same time, 23-90% of scale, 8-75% of carbon-containing raw materials and 1-2% of bentonite are fed. Based on the experimental data, subject to these proportions, the best elasticity and plasticity of the mixture are achieved, eliminating the presence of air porosities in it, which ensures uniform and homogeneous filling of the extruder chamber and, as a result, provides a high-strength briquette.

Next, the scale, carbon-containing raw materials and bentonite conveyor No. 2 is sent to the mixer for homogenization and stabilization of the composition. In the process of mixing, water is supplied to the mixer to moisten and plasticize the mixture with a 10% moisture content in the mixture.

Prepared homogenized mixture from the mixer is fed via conveyor No. 2 to the warehouse for sedimentation of the mixture, where it lasts from 8 to 24 hours, which is optimal to ensure the elasticity of the mixture.

The preliminary saturation with moisture of the hygroscopic elements of the mixture, namely bentonite, and their elimination of excess moisture during the sludge sedimentation contributes to the further qualitative mixing of the mixture with a binder (cement), which further ensures high physical and mechanical properties of the briquettes.

In addition, this mixing sequence ensures uniformity of the chemical composition of the manufactured briquettes in each batch of the product.

Press section. At the pressing site, the resulting mixture is fed with the addition of water and a binder in the form of cement into an extrusion press to obtain briquettes.

The prepared mixture from the stockpile of sludge with a front-end loader is loaded into the receiving hopper of the pressing line. From the receiving hopper through the screw feeder, the mixture enters the conveyor No. 3, through which it is fed into a twin-roll mixer.

From silo No. 3 to conveyor No. 3, simultaneously with the prepared mixture, 5% of cement is supplied to the twin-roll mixer, which is sufficient to ensure the required strength of the resulting briquette. During mixing, water is supplied to the mixer to plasticize the finished mixture and achieve a moisture content of 12-15%.

After mixing in a twin-roll mixer with cement and water, the mixture is fed into the extruder dosing device, in which it is pre-compacted, and fed into the vacuum chamber of the extruder. A low vacuum is maintained in the vacuum chamber from 760 to 25 mm Hg, from 1 × 10 ⁺⁵ to 1 × 10 ⁺¹ Pa.

To obtain a briquette using an extrusion press with a fixed front of the axis of the main extrusion screw. Unlike presses with a freely located front part of the axis, the press used allows for uniform flow rate and density of the initial mass when it is fed to the channels of the die plate along its entire plane, with guaranteed production of briquettes of uniform quality in terms of strength characteristics and specific gravity.

After passing through an extruder with a side pressure of 5.2 MPa, the finished product is fed by conveyor No. 4 to the finished briquette section (in the chest).

At the site of finished briquettes, a set of product strength of at least 5 MPa occurs. After curing (78 hours), finished briquettes are transported by a front-end loader to a finished goods warehouse to form a transport lot and ship to the consumer.

The invention is illustrated by the following examples.

Example 1. To obtain a briquette used mill scale (69%), carbon-containing material (24%), bentonite (2%) and as a cement binder (5%) with the addition of water. The chemical composition of the components and the resulting briquettes are shown in table 1.

After separating the scale with a -3 mm fraction and carbon-containing raw materials, they were mixed with bentonite in a mixer in a ratio of 10 kg of bentonite per 1 ton of charge. During the mixing process, water was fed to obtain a 10% charge moisture content.

The prepared homogenized charge was kept in stock for a charge of 12 hours. The prepared mixture from the warehouse for sludge and cement are simultaneously sent to a two-roll mixer. With stirring, water is supplied to plasticize the mixture and achieve a moisture content of 12%.

After mixing in a twin-roll mixer, the mixture is fed to the extruder dosing device for its preliminary compaction and fed into the vacuum chamber of the extruder. The pressure in the vacuum chamber is 50 mm Hg.

Then, the charge was passed through an extruder with a lateral pressure of 5.2 MPa, after which the resulting briquette was sent to the finished briquette section for building strength of at least 5 MPa for 78 hours.

Example 2. To obtain a briquette used mill scale of two industries (39% + 33%) fraction -3 mm, carbon-containing material (21%), bentonite (2%) and as a cement binder (5%) with the addition of water. The chemical composition of the components and the resulting briquettes are shown in table 2.

After separation, a scale of -3 mm fraction and carbon-containing raw materials were mixed with bentonite in a mixer in a ratio of 10 kg of bentonite per 1 ton of charge. During the mixing process, water was fed to obtain a 10% charge moisture content.

The prepared homogenized charge was kept in stock for a charge of 12 hours. The prepared mixture from the warehouse for sludge and cement are simultaneously sent to a two-roll mixer. With stirring, water is supplied to plasticize the mixture and achieve a moisture content of 12%.

After mixing in a twin-roll mixer, the mixture is fed to the extruder dosing device for its preliminary compaction and fed into the vacuum chamber of the extruder. The pressure in the vacuum chamber is 50 mm Hg.

Then, the charge was passed through an extruder with a side pressure of 5.2 MPa, after which the resulting briquette was sent to the finished briquette section for building strength of at least 5 MPa for 78 hours.

Ready briquettes correspond to the following physical properties (table. 3):

Thus, the obtained extrusion briquettes are high-quality carbon-iron-containing products for use as a component of the charge in blast furnace production.

Claims (4)

1. Briquette for blast furnace production, obtained by the method of hard vacuum extrusion, consisting of mill scale, 8-75% carbon-containing material, 1-2% bentonite and 5% cement, and containing, by weight. %: FeO <40 Fe ₂ O ₃ > 20 MgO 0.01-2.5 MnO 0.01-9.0 Cr ₂ O ₃ 0.01-1.5 FROM 0.1-75.0 S 0.01-0.5 SiO ₂ 0.1-15.0 TiO ₂ 0.01-0.1 CaO 0.1-7.0 Al ₂ O ₃ 0.01-1.5 impurities <2 the content of Fe _total is 10.0-58.0, compressive strength is not less than 5.0 MPa, specific gravity is not less than 2.8 kg / dm ³ , open porosity is not less than 10%, and the temperature of the onset of softening - not less than 1200 ° C. 2. The briquette according to claim 1, characterized in that the scale is used as a scale of a separate or different metallurgical industries.

Images