RU2398029C2 - Procedure for production of briquettes out of industrial dispersed ferroalloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to utilisation of small fractions of ferroalloys. Industrial dispersed ferroalloys are screened and small fractions of 10 mm and less are separated. Charge, made out of metered portions of small fractions of ferroalloys and binding, is mixed and compressed; produced briquettes are dried. Additionally, into composition of charge there is introduced vermiculite as adsorbent of low density and high absorbing capacity relative to water solution of binding or its solvent; vermiculite is introduced at amount of 2-20% of charge weight. Fluorite concentrate at amount of up to 7% of charge weight is introduced into composition of charge to facilitate solution of briquettes added to steel. To decrease interaction of solvent with siftings of ferroalloys a passivator in form of water solution of potassium bio-chromate at amount of up to 0.2% of ferroalloys powder weight is introduced into composition of charge.

EFFECT: production of durable briquettes out of small fractions formed at crumbling; increased degree of alloying elements absorption at their successive utilisation.

3 cl, 1 tbl, 1 ex

Description

The invention relates to metallurgy, in particular to the utilization of a small fraction of various materials by sieving and subsequent briquetting, in particular, sieving of ferroalloys after crushing them, followed by briquetting of a fraction of 10 mm or less, which, when directly alloyed with steel, has a very low absorption.

A known method of producing briquettes from industrial dispersed materials (ferrosilicon, fluorite concentrate), including preliminary granulation of the starting materials with an additive as a binder liquid glass, drying granules, pressing granules into briquettes and drying briquettes [1].

This method eliminates the sticking of the material during the pressing process and significantly increase the productivity and strength of briquettes, i.e. provides its manufacturability. The disadvantage of this method is that its implementation requires the use of additional equipment, includes a number of additional operations (pelletizing and drying pellets) and can be provided only in the production of briquettes from dusty waste in small batches.

A known method of producing briquettes from small fractions of silicon-containing ferroalloys, including the dosage of the material and binders, mixing, briquetting and drying [2].

The disadvantage of this method is that when liquid glass is used as a binder, it strongly adheres to the elements of the mixer and the pressing equipment, the mixture crumbles and has a low fluidity, which complicates the pressing process and does not provide high productivity. Immediately after the introduction of liquid glass, its interaction with silicon begins, accompanied by significant heat release, which also requires rapid processing of the mixture and limits the volume of the prepared molding mixture. The interaction of liquid glass with silicon before pressing leads to a decrease in its binding properties and strength of the briquette, the formation of a large amount of fines during transportation and the task of briquettes in the steelmaking unit, which reduces the degree of their absorption.

A known method of producing briquettes from ferrosilicon used in the smelting of low-carbon ferrochrome, in which ultrafine silica from electrostatic precipitators is used as a binder and an aqueous solution of caustic soda is introduced immediately before pressing [3]. This invention is the closest in technical essence and is taken as a prototype.

The disadvantage of this method is the use of ultrafine silica, which has a very low density and is prone to sticking under the influence of static electricity. This creates significant difficulties when mixing the mixture. In addition, the high activity of ultrafine silica requires rapid processing of the molding sand immediately after the introduction of an aqueous solution of caustic soda.

The problem to which the invention is directed, is to increase the degree of use of materials, including ferroalloys, by obtaining briquettes from small fractions formed in the process of crushing them.

The technical result that the invention provides consists in the development of a high-performance method for briquetting small materials, including ferroalloys, which allows one to obtain strong briquettes and increase the degree of assimilation of alloying elements during their subsequent use.

This is achieved by the fact that an additional material is introduced into the mixture — an adsorbent having a low density, developed surface and high absorption capacity in relation to a binder solution or solvent, in an amount of 2-20% of the charge mass. Vermiculite is used as an adsorbent.

When a solvent or a binder solution is introduced, they are predominantly absorbed by particles of vermiculite, which ensures high flowability of the molding mixture, reduces the interaction of the solvent material and the binder with the ferroalloy. When pressing, the solvent or solution is extruded from the particles of vermiculite, which leads to the bonding of the molding sand in durable briquettes.

An experimentally established relationship between the amount of introduced vermiculite and plant productivity, briquette strength and degree of absorption of silicon when alloying steel.

When aqueous solutions of bundles, in particular water glass, are introduced into the molding mass, they actively adhere to the elements of the mixing and pressing equipment, which requires constant cleaning, wetting of these surfaces with special substances that reduce the adhesion of the molding mixture, and masses ready for pressing have low flowability . This leads to a decrease in equipment productivity and an increase in the cost of briquette production. In addition, when processing screenings of silicon-containing ferroalloys using liquid glass as a binder, it interacts with silicon before pressing, which leads to a decrease in its binding properties and briquette strength, the formation of a large amount of fines during transportation and the task of briquettes into a steel-smelting unit, which reduces degree of their assimilation. In this case, it is necessary to significantly limit the volume of the molding material prepared for pressing, which also leads to an additional loss of productivity.

Expanded vermiculite has a developed surface and high moisture absorption capacity. With the introduction of water or an aqueous solution of a binder into the mixture, due to the capillary effect, the main part of the liquid components is absorbed by vermiculite, and the moldable mixture remains almost dry. This allows to significantly reduce the adhesion of the molding sand to the elements of the mixing and pressing equipment, to ensure high flowability of the molding sand, which leads to a significant increase in productivity of the equipment. In addition, in the case of briquetting screenings of silicon ferroalloys using liquid glass as a binder, the interaction of silicon with the binder before pressing is significantly reduced, which increases the strength of the briquette, the degree of assimilation, and the performance of the press equipment. During pressing, vermiculite particles are compressed and a binder solution or solvent is secreted into the surrounding space and provide reliable bonding of particles of the main components of the briquette.

The lower limit on the vermiculite content is determined on the basis that with a vermiculite content of less than 2.0% the required briquetting performance is not provided. The amount of adsorbent to absorb the binder is not enough, which leads to the adhesion of the molding sand on the elements of the mixer and briquetting installation, deterioration of the flowability of the molding sand and loss of performance. In this case, the briquette has unstable strength and degree of assimilation due to the interaction of moisture (ligaments) with silicon. The upper limit of 20% is due to a decrease in the strength of the briquette, a decrease in the degree of assimilation of silicon associated with slagging of the briquette due to the introduction of a significant amount of silicon, magnesium and aluminum oxides, which are part of vermiculite and significantly slow down its dissolution, and a drop in the productivity of the installation.

The introduction of slag components into the briquette composition, which includes vermiculite, as well as the interaction of ferroalloys with a solution of a binder or solvent, for example with water, with the formation of oxides of the corresponding metals, lead to slagging of the briquettes and slow their dissolution. To eliminate this undesirable effect, up to 7% fluorite concentrate is introduced into the briquette composition, which leads to a decrease in the melting temperature and viscosity of the oxide component, which helps to accelerate the dissolution and the degree of assimilation of alloying elements from briquettes. The upper limit on the fluorite content of 7% is determined from the fact that its addition in large quantities no longer has a significant effect on the dissolution rate of the briquette and the absorption of silicon and leads to a decrease in the amount of the alloying element in the composition of the briquette.

As noted above, when a binder or solvent (water) solution is introduced, screenings of the briquetted ferroalloy, in particular their dust fractions, interact with the formation of the oxide component, which impairs the dissolution of the briquette and reduces the degree of assimilation of the alloying element. To reduce the oxidation of screenings of ferroalloys with a solvent, a passivator is introduced into the mixture in the form of an additive of potassium chrompeak (potassium dichromate) in an amount of up to 0.2% by weight of the mixture. With the introduction of a larger amount of potassium dichromate, with the same passivating effect, there is a decrease in the strength of the briquette in its raw form, its transportability deteriorates, which leads to a loss in productivity.

The table shows the compositions of the proposed tested ferroalloy briquettes (2, 3), compositions that go beyond the requested limits for the content of vermiculite (4-5), potassium chromica (6) and example 1 is a prototype.

A specific example of the manufacture of briquettes based on 65% ferrosilicon

Ferrosilicon FS65% after crushing on the ShchDS-1-4 × 9 jaw crusher was screened on a GIL-42 screen with a fine fraction separation of 10 mm. Vermiculite was calcined at a temperature of at least 750 ° C. Then, the initial components: ferrosilicon, vermiculite, fluorite concentrate, were loaded into consumable bins and, after weighing, served in a mixer, where they were mixed for 20-25 minutes. After that, a bunch was introduced in the form of an aqueous solution of water glass with a density of 1.35-1.40 g / ml in the amount of 6% by weight of the mixture and an aqueous solution of potassium chromic peak based on the preparation of its content of 0.1% by weight of ferrosilicon and the mixture was further mixed in within 20 minutes to obtain a uniform consistency. The molding mixture from the mixer was set in the receiving hopper of the press. The briquettes were pressed with a diameter of F = 50 mm and a height of H = 50-60 mm produced on a PK-1200 press of a revolving type. Briquettes were dried in an oven at a temperature of 170 ± 10 ° C until a moisture content of not more than 1%.

Briquettes were loaded before draining the metal from the converter to the bottom of the ladle during smelting of steel 35GS. The assimilation of silicon from briquettes on the discharge from the converter averaged 82%, which is close to the degree of assimilation of silicon when using crushed ferrosilicon FS-65 with a piece size of up to 50 mm, equal to 89%.

Thus, a high-performance method has been developed for the disposal of small fractions of various materials, in particular ferroalloys, by introducing adsorbents having a developed surface, absorbing a solvent or a binder solution when mixing the starting components and releasing them when pressed into the molding composition, which allows obtaining strong briquettes and increase the degree of assimilation of alloying elements in their subsequent use.

Information sources

1. A.S. USSR No. 1786151, class C22B 1/243, 1990, bull. No. 1, 1993

2. Fedorenko N.V. and others. Rational use of substandard and dispersed fractions of ferroalloys. Theory and practice. - Chelyabinsk, South Ural State University, 1998, p. 152-165.

3. Patent RU 2156814 C1, 10.19.1999, publ. 09/27/2000, Bull. Number 27. - prototype.

Claims (3)

1. A method of producing briquettes from industrial dispersed ferroalloys, including sieving with separation of a fine fraction of 10 mm or less, dosing a fine fraction of ferroalloys and a binder, mixing the mixture, pressing and drying the briquettes, characterized in that vermiculite is additionally introduced into the mixture as an adsorbent having a low density and high absorption capacity in relation to an aqueous solution of a binder or its solvent, in an amount of 2-20% by weight of the mixture. 2. The method according to claim 1, characterized in that to facilitate the dissolution of the briquettes when introduced into steel, fluorite concentrate is introduced into the composition of the mixture in an amount up to 7% by weight of the mixture. 3. The method according to claim 1, characterized in that to reduce the interaction of the solvent with screenings of the ferroalloys, the passivator is introduced into the mixture in the form of an aqueous solution of potassium dichromate in an amount of up to 0.2% by weight of the ferroalloy powder.