RU1786105C - Method of preparing burden for melting fluoride-oxide fluxes - Google Patents

Abstract

Usage: in metallurgy more specifically - in the smelting of fluoride-oxide fluxes. SUMMARY OF THE INVENTION: It is proposed that finely divided charge materials be pre-briquetted by mixing the latter with a 45-56% solution of technical ligno sulfonates (LST) with a density of 1.20-1.30 g / cm3 and a calcium oxide content of 1.0-5.6 wt.%. The flow rate of the binder is determined by the inverse ratio to the specific pressing pressure (in kg / cm2) of 50-114. The mixture is briquetted on a roller press, then subjected to joint drying and carbonization at a temperature of 150-250 ° C for 60-120 minutes. 3 tab ..

Description

The invention relates to ferrous metallurgy, in particular to the production of fluoride-oxide fluxes for welding and electroslag remelting, and can be used in various engineering industries in the production of fluxes of both welding and electroslag assortment.

Considerable attention is currently being paid to the use of environmentally friendly technologies. At the same time, the technology for smelting fluoride-oxide fluxes is based on the use of pulverized charge materials supplied to the furnace by pneumatic conveying to tubes, which significantly worsens the environmental situation.

A known method for the production of briquettes from dust from steel mills, in which dust containing more than 15 wt.% Metallic iron, is heated to 500 ° C in rotary kilns with external heating, briquetted in an inert atmosphere on roller presses at pressures of 60-150

kN / cm roll width. Then the briquettes are cooled with air to 130 ° C 1.

However, this method is not effective for briquetting dusty materials of ore origin, since it does not require preliminary sintering (or the creation of conditions for it), as well as creating an inert atmosphere .......... - The closest technical solution to The invention is a method for preparing a charge, comprising briquetting the components with the addition of a binder, which quickly loses its binder properties at high temperatures. The binder used is molasses black and lime, tall oil or lignite 2.

This method of preparing the charge is intended for the production of flux from briquettes. in this case, the technology for producing briquettes ensures the destruction of the briquettes when they are introduced into the slag melt, which is necessary to speed up the process of dissolving lime in the slag. However, this is disadvantageous.

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com in the industrial production of fluxes by the electrothermal method. In addition, the prototype provides for the use of scarce and expensive binders, for example, tall oil, which 5 are characterized by high viscosity, which does not allow to achieve high quality mixing of the binder with the components of the mixture and, therefore, reduces the strength characteristics of the obtained briquettes. - 10 hours of free lime in quality:. binder leads to swelling of the briquette when stored in air, because CaO is poorly wetted by a liquid binder and, under atmospheric conditions, its hydride occurs.

 ratacy to Ca (OH) 2, which also does not contribute to the production of durable briquettes. In addition, the disadvantage of the prototype is the low thermal strength of the briquettes, due to the low temperature resistance of the binder used, as well as. ., the fact that this method does not provide conditions for the occurrence of carbonization processes. This method allows to obtain briquettes with a CaF2 content of 25 10 to 55 parts by weight. However, it does not stipulate the conditions for the production of briquettes from other dusty materials, for example, fluorite concentrate, magnesite, sludge from flux-smelting production, etc. Moreover, the use of a briquette burnt by this method as a flux is used. Ca leads to the development of processes of evaporation of fluorine-containing components of the slag when this flux is introduced into the smelting unit 35, which is caused by thermal dissociation of calcium hydroxide with the subsequent formation of a volatile hydrogen fluoride compound. This method of preparing the charge does not allow 40 to reduce the component loss by dust removal and evaporation, as well as to increase the yield of suitable flux.

The purpose of the invention is to reduce losses ;; components by dust removal and evaporation, and 45 also increase the yield of flux,

. The goal is achieved in that. The pulverized components of the flux-smelting production of a fraction of more than 10 microns and, with a specific surface area of 5000-25000 cm2 / g 50., are mixed with a 45-55% solution of lignosulfonates with a technical density of 1.20-1.30 g / cm and calcium oxide content. 1.0-5.0 May.%, While the flow rate of the binder is determined by the inverse ratio of tow-55

 pressing pressure of 50-114, followed by briquetting the mixture on: a roller press with joint drying and carbonization of briquettes at a temperature of 150-250 ° C for 60-120 minutes.

It is known to use briquettes in the smelting of a barium-containing alloy, where the mixture included barite concentrate, gas coal, quartzite and coke. A mixture of barite and coal is briquetted. However, the carbon content is a harmful impurity in fluxes. In addition, briquetting of aluminum hydroxide using caustic sodium and liquid glass as a binder is known. However, the use of indicated (b1x, binders in preparing the charge for smelting fluoride-oxide fluxes is not possible, because The content of these components in the finished flux is strictly limited.

A method is known for the pelletizing of fluorite concentrates using, as a binder, liquid glass. However, the paper presents materials for the production of fluorite pellets. Pellet production is currently less efficient. Briquetting batches, unlike stacking, makes it possible to obtain briquettes with a constant density and moisture content at a significantly lower consumption of raw materials, and is also a more productive process. ...,:,;: ..--.

According to the proposed method, dusty materials of flux-smelting production of a fraction of more than 10 μm and with a specific surface of 5000-25000 cm2 / g are briquetted. The use of charge materials with a fraction of more than 10 microns promotes better wetting of the particles. The charge is a binder component. The use of fractions less than 10 microns leads to heterogeneity of the resulting briquette. In addition, the specific surface of the materials used has a great influence on the quality of the prepared mixture. Briquetting a mixture with a specific surface area of less than 5000 cm2 / g worsens the conditions for producing uniform density briquettes. Briquetting of dusty materials with a specific surface of more than 25,000 cm / g adversely affects the thermal strength of the resulting briquettes due to their excessive ductility.

An advantage of the proposed method for preparing the charge, in contrast to the prototype, is the use of a binder of 45-55% solution of technical ligno-sulfonates (LBF) with a density of 1.20-1.30 g / cm3 and calcium oxide content. 1.0-5.0 wt.%, Which provides the necessary viscosity of the binder and improves the wetting conditions of the dusty particles when they are mixed. The use of LCF with a concentration of less than 45% reduces the curing properties of the binder because of a decrease in adhesion. The use of LFB with more than 55 percent content in solution degrades the quality of the prepared mixture due to an increase in its sulfur content.

Mixing the mixture with LFD with a density of less than or more than 1.20-1.30 g / cm respectively reduces the processability of the briquetting process, since the yield of suitable briquettes decreases.

In addition, the advantage of the proposed method of preparation of the charge is the introduction of calcium oxide in the composition of the LST solution, which, unlike the prototype, does not lead to a decrease in the strength of the obtained briquettes, since CaO hydration occurs preliminarily in the composition of the binder according to the reaction

CaO + H20 Ca (OH) 2 (1)

The latter contributes to the hardening of the briquette due to the carbonation process.

The content of calcium oxide in the LST solution is regulated by a further technological redistribution. At a content of less than 1 wt.%, The CaO effect on the strength characteristics of the briquettes is low, which is due to its low content. The use of LFB as a binder with a CaO content of more than 5 wt.% Leads to an increase in the latter in the composition of the final product (fluoride-oxide flux AN F-6) over the standard defined by the requirements of technical documentation. The introduction of CaO in the composition of the LFB and mixing it with the components of the charge also contributes to blocking the grain boundaries of the obtained briquette, by which the prepared mixture is reflowed into the fluoride-oxide flux during further technological redistribution.

The flow rate of the binder is determined by the inverse ratio to the specific pressing pressure of 50-114. The recommended specific pressing pressure for the dust-like components of the flux-smelting production of a fraction of more than 10 microns is 600-800 kg / cm2. At the same time, depending on the moisture content of the starting components, the lower limit of the specific pressing pressure may be 400 kg / cm2. A higher pressing pressure helps to reduce the consumption of binder LBT and, conversely, lowering the pressure of the pressing helps to increase the consumption of binder to obtain a strong briquette. In accordance with the inverse multiplicity, the consumption of LFW is 7-12 wt.% Of the weight of the charge. At the same time, reducing the consumption of LST

less than 7 wt.% leads to a deterioration in the briquetting of charge materials, and also does not sufficiently block calcium grain boundaries, which leads to increased losses of charge materials at this and subsequent limits. An increase in the binder consumption of more than 12 wt.% Is irrational, since the material acquires excessive ductility and the strength characteristics of the obtained briquettes are not ensured. Briquetting of the mixed charge is carried out on rolls of a press equipped with forming cells. After completion of the forming process, the briquettes are co-dried and carbonized at a temperature of 150-250 ° C for 60-120 minutes.

In contrast to the prototype proposed

0 method of preparation of the mixture provides high thermal strength of the obtained briquettes, due to the joint occurrence of drying and carbonization processes, since carbonization is natural in air

5 is slow because the carbon dioxide content in the atmosphere does not exceed 0.04 wt.%. The briquettes are dried in a conveyor type dryer. Natural gas is used as a heat carrier. At

0 carbon dioxide forms carbon dioxide

CH4 + 202 CO2 + 2H20pairs (2)

In this case, the carbonization process proceeds in two successive phases: 5 1) evaporation of mechanically mixed water and gradual crystallization of Ca (OH) 2;

2) carbonization of calcium hydrate during the absorption of COa from the atmosphere of the drying oven 0 by the reaction:

Ca (OH) 2 + CO2 + pN20 CaCO3 + (p + 1) Y20 (3) Carbonization promotes the formation of a branched carbarnate 5th skeleton in the briquette, which increases the strength properties,

Drying temperature (carbonization) of less than 150 ° C is undesirable, since it reduces the intensity of the process in the cementation of 0 briquettes. Exceeding the drying (carbonization) temperature of more than 250 ° C leads to burnout of the binder and, consequently, to a decrease in the strength characteristics of the briquettes.

5 The drying time of less than 60 minutes does not ensure the completeness of the processes of briquetting carbonization. For more than 120 minutes, drying the briquettes is irrational, since during this period it is not achieved; Strength required.

According to the claimed method for preparing the charge, dusty materials of flux-smelting production can be briquetted: fluorite concentrate, caustic magnesite, alumina in the composition of fluorite and magnesite, sludges of flux-smelting production and other materials. The binder, ligno-sulpho-technical, must be manufactured and supplied in accordance with the requirements of OST 13-183-83.

The requirements for the charge materials used must be satisfied in terms of chemical composition, humidity, and also the upper limit of the content of particulate matter. For example, the requirements for the chemical composition: composition for fluorspar concentrates (extract from GOST 76-18-83) are given in the table. 1. .;

2.3. The moisture cash fraction in flotation plank and spar concentrate of all grades should not exceed i, 0%.

2.4. In flotation, fluorspar concentrate of all grades, the mass fraction of particles greater than 0.14 mm should not exceed

Yu%. .:.; :; ,:. .

The advantages of the proposed method for preparing the charge for smelting fluoride oxide fluxes are the reduction of component loss by dust removal and evaporation at the smelting stage, the improvement of the environmental situation at workplaces, as well as the increase in the yield of flux. In addition, the advantages are the mixing of the components with a binder, which contains pre-hydrated calcium oxide, which subsequently allows the briquette to be hardened by carbonization if the heat carrier is correctly selected.

The technological line for the preparation of pulverulent materials includes dosing with a component. from dosing hoppers, transportation by auger through the brooms to the paddle twin-shaft mixers m. Injection into the mixer of a binder of LFD with a density of 1.20-1.30 g / cm3. Subsequently, the charge materials are mixed, moistened and fed through the tubes to the receiving hopper of the briquetting press. Roller type press equipped with shaping cells on bandages. The mixture enters from above into the roll space, is pressed into a force of 600-800 kg / cm2, and the crude briquettes fall to the screen. The tarp then returns to the receiving hopper with the elevator conveyor. Subsequently, the briquettes are transported by tape to a conveyor dryer, where they are dried and carbonized, after

what briquettes come to the finished goods warehouse.

Under laboratory conditions, the process chain was used to briquette the dusty materials of the smelter production: fluorite concentrate, magnesite, fluorite with alumina, sludge from the smelter production.

The technological parameters of the proposed method of preparation of the mixture are presented in table. 2.

Each component was tested in five variants. Data on test results for each type of material are given in table. 3.

For greater clarity in the table. 3 except strength characteristics, the test results of the obtained

briquettes in the subsequent redistribution - obtaining fused fluoride-oxide fluxes in electric furnaces.

Based on the tests carried out, it can be concluded that options 2-4 have the optimal technological parameters of briquetting, which corresponded to a specific briquetting pressure of 600-800 kg / cm2 with the remaining parameters given in the characterizing part of the claims. In this case, option 1 is characterized by the minimum values of strength characteristics. Testing of briquettes obtained according to option 5 is characterized by a decrease in strength characteristics for all types of materials due to the re-pressing of the charge.

When using prepared

batch for smelting fluoride-oxide fluxes, a reduction in briquette J06 consumption was obtained due to a decrease in the components loss by dust removal and evaporation (Table 3).

The expected economic effect of the preparation of charge materials by briquetting in Nikopolsky conditions

ferroalloy plant will be more than 205 thousand rubles. in year.

Claims (1)

SUMMARY OF THE INVENTION A method for preparing a charge for smelting fluoride oxide fluxes, the method comprising briquetting of dust-like components of flux-smelting production with the addition of a binder, with the aim of reducing the loss of components by dust removal and evaporation and to increase the yield of suitable flux, a 45-55% solution of technical ligno-sulfonates of technical grade (LST) with a density of 1.20-1.30 g / cm3 and a calcium oxide content of 1.0-5.0 wt.%, which mixed with dusty components fractions of more than 10 μm and a specific surface area of 5000-25000 cm2, while the flow rate of the binder is determined by the inverse ratio of the bulk pressing pressure in kg / cm2 50-114, and briquetting is carried out on a roller press, followed by joint drying and carbonization of the briquettes at a temperature of 150-250 ° C for 60-120 minutes. Table 1  Option corresponding to the prototype method. Table 2 Table 3