RU2506325C2 - Method for producing extrusion-type briquette (breks) for metal melting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, and namely to iron-ore raw material agglomeration methods. Extrusion-type briquettes for metal melting are produced by a method of stiff vacuum extrusion from charge mixture containing an iron-ore concentrate and/or ore, carbon-containing materials, a mineral binding agent, and if required, iron- and/or iron and carbon containing wastes and fluxing additives. A homogenised mixture is continuously supplied to an extrusion machine; air is removed from it by vacuum processing and mixture is squeezed through a variety of holes in a drawing-block of the extrusion machine so that plastic rods with microcracks in their upper layer are obtained. They are transported and piled with fragmentation during those operations for 2-3 briquettes, the dimensions of which are controlled by changing, considering density of the rods, the surface area and the shape of holes in the drawing-block.

EFFECT: invention allows producing agglomerated charge component of the required chemical composition at minimum consumption of a binding agent having optimum dimensions to be used in blast, steel-making and ore-treatment furnaces and in cupola furnaces with high hot strength and reductibility.

3 cl, 2 ex

Description

The invention relates to ferrous metallurgy, in particular to methods for sintering iron ore raw materials, and can be used in the preparation of a charge for smelting metal in steelmaking, ferroalloy and blast furnaces.

A technical solution is known - a method for producing briquettes for metal smelting having the correct geometric shape and prepared from finely dispersed iron-containing waste, finely divided carbon-containing material and a binder, which is used as a mechanical mixture of natural materials - loam, clay or feldspar and sodium carbonate [RF Patent No. 2154680 , С22В 1/243, 7/00, 2000, BIPM No. 23]. The briquette for smelting metal according to a known technical solution is obtained by pressing a mixture of these materials moistened with an aqueous solution of water glass, followed by drying of the resulting briquette. The disadvantage of this known technical solution is that the briquette for metal smelting, obtained by the described technology, does not have sufficient hot strength, which does not allow it to be used as a charge component in blast furnaces and ore-thermal furnaces. This is also hindered by the presence in the briquette of alkali metals (water glass), which contribute to the dust formation in shaft furnaces.

This drawback is eliminated in another well-known technical solution, which is a method for producing agglomerated material from a mixture of small iron-containing waste from metallurgical production, crushed carbon-containing material and alumina cement by making concrete from this mixture and crushing it into pieces necessary for loading into a blast furnace, coarseness [DE 3727576, MKI C22B 1/243 of 08/19/1987]. A trifle formed during crushing of concrete is used in the sinter mixture. The latter is a disadvantage of this known technical solution, as it complicates the technological scheme and makes it multi-stage and costly.

This drawback is eliminated in another well-known technical solution, which is a method for producing a briquette component of a blast furnace charge by vibrocompression from a mixture comprising carbon-containing materials, iron-containing materials, fluxing additives and a mineral binder, in which the ratio of carbon to iron is in the range of 0.35- 0.6, basicity is in the range of 0.3 ... 1.6, the fineness of the materials included in the charge does not exceed 10 mm, the mass of the briquette is 1.5-8 kg, and the ratio of the maximum and minimum sizes The briquette number does not exceed 1.2 [RF Patent No. 2241760, MKI C1, 7C21B 5/00, C22B 1/243. 2003.07.03. Published 2004.12.10].

The disadvantage of this known technical solution is the low productivity and discreteness of the method for producing briquettes, as well as a complex logistic scheme for their movement from the vibrating table to the finished goods warehouse, which requires the use of forklifts and is not amenable to automation. The increased consumption of cement in this method increases its cost. In addition, the sizes of the resulting briquettes significantly exceed the optimal sizes of pieces of charge materials used in ore-thermal, induction and blast furnaces.

An object of the invention is the elimination of these disadvantages of the known technical solutions and the provision of an agglomerated component of the charge of the required chemical composition with a minimum consumption of a binder that has optimal dimensions for use in blast furnaces, steelmaking, ore-heating furnaces and cupolas, as well as having high hot strength and recoverability.

The solution to this technical problem is achieved by the fact that the method of producing an extrusion briquette (BREX) for metal smelting, including the preparation and homogenization of a charge mixture from a mineral binder, iron ore concentrate and / or ore, carbon-containing materials and, if necessary, iron and / or iron-carbon waste and fluxing additives, continuously feeding the resulting mixture into the extruder, removing air from it by evacuation and forcing the mixture through an extruder die having a plurality of holes minutes shape and size to obtain plastic rods of predetermined length and cross-section defined by their density, shape and size of holes in the spinneret, followed by fragmentation of the rods during their transportation and congestion 2-3 BREKSa optimal size for smelting metal.

The solution of the indicated technical problem is also achieved by the fact that the dimensions of the BREXs are increased or decreased by increasing or decreasing the area of the holes in the die.

The solution of this technical problem is additionally achieved by the fact that with oval holes in the die, the length of the BREXs is increased by positioning the major axis of the holes vertically, and reduced by placing it horizontally.

The technology of agglomeration of dispersed materials by hard vacuum extrusion is known. This technology, in particular, is widely used in the production of bricks from a mixture of clay-based mixtures (A.Ya. Khavkin, RZ Berman. Brick factories of low power. Building materials. 2000, No. 4, p. 18-19). Its essence is to prepare a wet mixture based on clay, continuously supplying the mixture to the extruder, removing air from the mixture by vacuum and forcing the mixture under pressure through a single rectangular hole in the extruder die with a section of (40-50) × (60-80) mm, which continuously comes out a dense plastic bar. Raw bricks are obtained by periodically instantly cutting the beam exiting the die with a multi-wire cutter into equal parts with a length of 160-200 mm. Thus, according to the principle of operation, this technology is continuous and provides the strength of “raw” bricks necessary for their multilayer laying on pallets and transportation in the furnace for hardening firing, and eliminates the formation of waste and the need for recycling. This fundamentally distinguishes the technology of rigid vacuum extrusion from the discrete briquetting technology by vibropressing and from the continuous technology of pressing in rolls, where recycling of a significant share of return is inevitable.

Laboratory studies have shown the possibility of applying extrusion briquette pressing technology to obtain an extrusion briquette (BREX) for smelting metal from a mixture of mineral binders, natural iron ore materials, carbon-containing materials, iron and / or iron-carbon dispersed wastes and fluxing additives. When a die is used in an extruder with many round, oval or other holes, cantilever dense plastic rods are continuously formed at the exit from it. As a result of the growth of the bending moment arising under the influence of the increasing mass of the cantilever rods, upon reaching the critical mass and length upon exiting the die, the rods break off. The critical length of the rods and the dimensions of the obtained BREXs can be controlled by affecting their density and ductility, as well as by changing the shape and size of the holes in the die.

The use of hard vacuum extrusion sintering technology in relation to natural iron ore materials and man-made iron and / or iron-carbon containing materials in order to obtain BREKS for metal smelting having specified sizes, chemical composition and metallurgical properties, ensuring their effective use for metal smelting together with any other known components of the charge or separately, the applicant is not known.

The invention consists in the following. The application of the method and technology of rigid vacuum extrusion for agglomeration of a mixture of mineral binder, iron ore concentrate, and / or iron ore, carbon-containing materials and, if necessary, iron and / or iron-carbon waste and fluxing additives provides rods with extremely dense output from the die ( 2.0-2.2 g / cm ³ ) and a plastic structure having a length of 110-180 mm This length is determined by their density, i.e. their composition, as well as the shape and size of the holes in the die. The high density of the rods continuously emerging from the openings of the die in the form of cantilevers causes, under the action of a bending moment (due to the increasing mass of the rods), the formation of transverse microcracks in the upper layer of their bodies, and then, upon reaching a critical mass and length, the rods break off and fall to the conveyor transporting them to the stacker. During transportation, stacking and further reloading operations, microcracks in the core of the rods increase and the rods break with the formation of 2-3 BREXs having dimensions (25-40) × (40-60) mm, which ideally meet the requirements for the components of the charge for smelting metal in steelmaking, ore-thermal and blast furnaces, as well as cupolas. In this case, the dimensions of the BREXs can be controlled by affecting the density and ductility of the rods at the exit of the die by changing the component composition of the briquetted mixture, as well as by changing the size, shape and location of the holes in the die. To increase the size of the BREX, increase the size of the holes and vice versa. When using oval holes to increase the length of the BREXs, the oval holes in the die are positioned vertically, to reduce the length - horizontally.

The invention is illustrated by the following examples.

Example 1. BREKS - for the smelting of metal was obtained by mixing Portland cement, iron ore concentrate, scale, blast furnace sludge, steam coal and lime in a ratio of 7: 66: 5: 10: 10: 2. After homogenization, the mixture was fed into a laboratory extruder, the mixture was evacuated by creating a pressure of not more than 10 Pa in the extruder vacuum chamber, and the mixture was continuously pressed with a pressure of 3.4 MPa through a die with a round hole with a diameter of 25 mm. A dense plastic rod continuously exiting the die when it reaches a length of 115-130 mm breaks off. The rods were divided into 3 BREX 40-45 mm long. The crushing strength of the obtained BREXs after aging for 48 hours was 4.5-5.0 MPa. After heating the BREKSs to a temperature of 1200 ° C in an atmosphere of 50% hydrogen and 50% nitrogen at a rate of 500 ° C per hour, the metallization degree was 87.5%. In the process of heating, BREKS completely retained its shape.

Example 2. BREX, obtained also as in Example 1, was placed in a crucible with molten iron and slag, which had a temperature of 1480 ° C. Within 24 minutes, the iron oxides in the BREKS were reduced by carbon, the iron was carbonized and melted, the waste rock of the BREKS components turned into slag, the BREKS was completely assimilated with the melt in the crucible.

Example 2. BREXs - for metal smelting, they were obtained on a semi-industrial briquetting line by mixing Portland cement, iron ore, blast furnace slurry, converter sludge and coke breeze in a ratio of 6: 30: 60: 4. After homogenization, the charge mixture was fed into the extruder, air was removed from the mixture by creating a pressure in the vacuum chamber of the extruder of 10 Pa or less, and the mixture was continuously pressed through with a pressure of 3.5-3.6 MPa through a die with round holes with a diameter of 25 mm. Dense, plastic rods continuously cantilever coming out of the die upon breaking the critical length (130-160 mm) broke off, fell onto the conveyor and transported to the stacker. A day later, the rods were picked up from the stack by a forklift and moved to the finished goods warehouse, where they were again stacked. During overloading, the rods were broken into 40-60 mm long BREXs with virtually no fines. Ready BRECs were fed into the bunkers of the blast furnace. The proportion of BREKSs in the charge of a blast furnace during the smelting of cast iron was 80%. The replacement of iron ore in a blast furnace charge with BRECs led to a reduction in coke consumption by 150 kg / t both due to the carbon contained in BRECs and replacing carbon coke in direct iron reduction reactions, and due to the removal of crude limestone from the charge due to the high basicity of BRECs .

Thus, the method of producing an extrusion briquette (BREX) for smelting metal according to the invention ensures the achievement of the technical task.

Claims (3)

1. A method of producing extrusion briquettes for metal smelting by hard vacuum extrusion from a charge mixture containing iron ore concentrate and / or ore, carbon-containing materials, mineral binders, and, if necessary, iron and / or iron-carbon waste and fluxing additives, characterized in that that carry out a continuous supply of a homogenized mixture to the extruder, removing air from it by evacuation, forcing the mixture through many holes in the extruder die to obtain plastic rzhney microcracks in their upper layer, their transportation and stacking fragmentation during these operations 2-3 preform dimensions are controlled by changing, with the rod density, area and shape of the holes in the spinneret. 2. The method according to claim 1, characterized in that the dimensions of the rods increase or decrease by increasing or decreasing the area of the holes in the die. 3. The method according to claim 1, characterized in that with oval holes in the die, the length of the rods is increased by placing the large axis of the holes vertically, and reduced by placing it horizontally.