RU2799597C1 - Method for processing zinc-containing materials - Google Patents

Abstract

FIELD: processing of technogenic formations.

SUBSTANCE: invention relates to the extraction of hard-to-recover zinc forms from dust and sludge from aspiration of industrial production. An initial mixture is prepared from a zinc-containing material, a solid carbonaceous reducing agent and a carbonate-containing flux, agglomerated by pressing, and the agglomerated mixture is subject to the Waelz process. Carbonate-containing flux is introduced into the initial mixture in an amount of (0.9-1.7):1 to the mass of zinc-containing material. The resulting mixture is homogenized by joint grinding to a specific surface area of the components from 3000 to 5500 cm²/g. Pressing is carried out at a pressure of 50 to 300 MPa, and the Waelz process is carried out at a temperature of 1100-1350°C.

EFFECT: zinc extraction from hard-to-recover sulphide forms from technogenic formations.

6 cl, 13 tbl, 2 ex

Description

The invention relates to the processing of technogenic formations of ferrous and non-ferrous metallurgy and other industries and can be used to extract hard-to-recover forms of zinc from dust and sludge from aspiration of industrial production.

A known method of extracting zinc by Waelz, which consists in introducing coke into a zinc-containing mixture and heating the mixture in a rotary kiln to a temperature of 1300 ° C, followed by trapping zinc oxide from the resulting clinker (Lakernik M.M., Pakhomova G.N. Metallurgy of zinc and cadmium. M : Metallurgizdat, 1969, pp. 393-409). The disadvantage of this method is the formation of accretion on the walls of the furnace due to partial melting of the clinker at temperatures of 1200-1250°C.

Known is the “Method of Waelzization of zinc-containing materials” (RF patent 2122596, publ. 11/27/1998), in which calcium-containing flux is fed into the furnace by blowing it with high pressure air (2-6 atm) from the discharge end of the furnace into the clinker formation zone in amount of 5 to 10% calcium oxide by weight of clinker. EFFECT: invention makes it possible to reduce build-up formation, increase lining durability and zinc yield. The disadvantage of this method is the uneven distribution of calcium oxide in the clinker being calcined, which can lead to the formation of local low-melting zones in the clinker.

A known method of disposal of dust from electric furnaces (RF patent 2484153, publ. 06/10/2013), in which the dust of electric furnaces is agglomerated together with a crushed carbonaceous reducing agent and a binder material in the form of pellets or briquettes, they are dried, heated and roasted in a rotary kiln together with a lumpy solid reducing agent at a temperature of unloaded materials of 700-1000°C, cooling gases and trapping dust from them containing zinc and lead fumes. In this case, the dust of electric steel-smelting furnaces before agglomeration is preliminarily mixed with lime-containing material and crushed carbonaceous reducing agent in an amount exceeding the stoichiometrically necessary carbon content for the reduction of iron, zinc and lead oxides by 1.5-2.0 times. The mixture is moistened to a water content of 8-11%, kept for 1-3 hours, and the resulting pellets or briquettes are loaded into the furnace together with a lumpy solid carbonaceous reducing agent with a particle size of 0-20 mm in an amount of 200-500 kg per ton of dust from electric furnaces. In this invention, the lime-containing material is mixed with the dust before firing, which makes it possible to evenly distribute the lime throughout the volume of the pellet and increase its reactivity. The disadvantage of the claimed invention is the use of a lumpy reductant, which leads to a significant overrun of the reductant.

The closest in technical essence and the achieved effect to the claimed invention is the "Method of pyrometallurgical processing of zinc-containing materials" (RF patent 2244034, publ. 01.10.2005), in which a mixture of zinc-containing material and a solid carbonaceous reducing agent is agglomerated, followed by agglomeration of the agglomerated mixture together with a solid carbonaceous reducing agent, wherein said mixture contains fine fractions of limestone in an amount of 2-10% by weight of the zinc-containing material, and the agglomeration of the mixture is carried out by pressing it, and before the mixing operation or simultaneously with it, the zinc-containing material is crushed. By grinding the raw mixture and pressing it, an increase in the zinc content in weltz oxide, a reduction in the consumption of a carbonaceous reducing agent, and a simplification of the technology for processing zinc-containing materials are ensured. The disadvantage of this invention is the lack of grinding and pressing parameters, and the amount of limestone introduced is not enough to extract hard-to-recover sulfide forms of zinc. It has been established that the value of pressing pressure has a significant effect on the kinetics of topochemical reactions, which is the zinc sublimation reaction. With increasing pressure. pressing up to 300 MPa, the degree of metallization increases from 34.6% to 71.9%, and the temperature of the onset of metallization shifts to the low temperature region.

It is known that zinc in technogenic wastes of metallurgical production can be found not only in the oxide form, for example, in copper slags, zinc is in the sulfide form (ZnS), in blast-furnace dust and sludge in the form of sphalerite ZnS and goslarite ZnSO ₄ ⋅ 7H ₂ O During the neutralization of some chemical production wastes, zinc in the sulfide form (ZnS) and gypsum dihydrate are formed in the sludge. In our country, such sludge is found in enterprises for the production of synthetic fibers. The main reason for the loss of zinc in the process of processing man-made waste is the impossibility of curing hard-to-recover forms (zinc ferrite, zinc silicate, zinc sulfide) by waelzation.

The technical result of the present invention is the creation of a method for the extraction of zinc sulfide forms by Waelz, which provides the extraction of hard-to-recover zinc sulfide forms from technogenic formations.

The specified technical result is achieved by the fact that in the method for processing zinc-containing materials, including the preparation of the initial mixture of zinc-containing material, solid carbonaceous reducing agent and carbonate-containing flux, agglomeration of the resulting mixture by pressing, wales of the agglomerated mixture, according to the invention, the carbonate-containing flux is introduced into the initial mixture in an amount ( 0.9-1.7):1 to the mass of zinc-containing material, the resulting mixture is subjected to homogenization by joint grinding to the specific surface of the components from 3000 cm ² /g to 5500 cm ² /g, pressing is carried out at a pressing pressure of 50 MPa to 300 MPa , and Waelzation is carried out at a temperature of 1100-1350°C.

As a zinc-containing material in the proposed method, dust and sludge from aspiration of industrial production are used, and a solid carbonaceous reducing agent is introduced into the initial mixture in an amount of (0.1-0.3):1 by weight of the zinc-containing material.

At the same time, if magnesium carbonate (magnesite) is used as a carbonate-containing flux, then it is introduced into the initial mixture in an amount of (0.9-1.25): 1 to the mass of zinc-containing material, when using dolomite as a carbonate-containing flux, then it is introduced into the raw mixture in the amount of (1.0-1.25):1, and when using limestone - in the amount of (1.1-1.7):1.0.

The extraction of zinc, which is in the technogenic waste in the oxide form, is possible due to the implementation of the reaction at a temperature above 1100°C,

Since in some technogenic formations zinc is in the sulfide form, its decomposition by carbon is possible by reaction at a temperature above 2000 ° C

However, at high temperatures (2000°C), the implementation of such a technology in practice will require the use of special high-temperature units (for example, arc furnaces), which is not economically feasible.

The implementation of exchange reactions with the transformation of the sulfide form of zinc into oxide is possible with metals that are in the series of voltages of metals to the left of zinc (metals with a higher electron affinity: Li, K, Ba, Sr, Ca, Na, Mg, Al, Mn).

From an economic point of view, Ca and Mg salts, which occur naturally in the form of limestone, magnesite, and dolomite, are the most attractive for the conversion of the sulfide form of zinc into oxide. When limestone is used to decompose zinc sulfide and sublimate zinc, the following reaction occurs

This reaction, when heated, proceeds in several stages. When heated to a temperature of 720 ° C, the decomposition of limestone begins according to the reaction

The decomposition of limestone is completed at a temperature of 920°C. Above this temperature, the exchange reaction proceeds

When zinc oxide appears, carbon begins to interact with it and completes the decomposition of zinc oxide according to reaction (1).

Thermodynamic analysis of reaction (3) indicates that its occurrence, as well as reaction (1), is possible above a temperature of 1100°C. The calculation of the stoichiometric ratio of zinc sulfide and calcium carbonate according to reaction (3) indicates that in order to extract 1% ZnS, 1.02% CaCO ₃ should be introduced into the raw mixture. The content of zinc in sludge from the production of synthetic fibers varies with depth and reaches 23.0%, which is 34.4% in terms of zinc sulfide. To transfer such an amount of zinc sulfide to oxide, at least 35.0% CaCO ₃ must be introduced into the composition of the raw mixture, which is 19.6% in terms of CaO. In known inventions, a much smaller amount of lime is introduced. In addition, since the zinc extraction reaction belongs to topochemical reactions, the rate of which depends on the area and force of contact of the reactants, the raw mixture before roasting, after the introduction of carbonates and coke, must be homogenized by joint grinding and briquetting with sufficient pressing forces.

When implementing the claimed method, the raw mixture is first homogenized, consisting of a zinc-containing material with carbon-containing additives (coke breeze) in an amount of (0.1-0.3): 1 to the mass of the zinc-containing material and calcium (magnesium) carbonates by their joint grinding to a specific surfaces from 3000 cm ² /g to 5500 cm ² /g. Due to this preparation of the initial mixture, a strong contact of the zinc-containing material with carbon-containing and carbonate additives is ensured during subsequent briquetting, which facilitates the flow of solid-phase processes of zinc desulfurization and sublimation during heating of the briquettes. When the content of carbon-containing material is less than 10% by weight of zinc-containing material, the required degree of zinc removal is not ensured, and at a content of more than 30%, the cost of the briquette rises. The resulting grinding product is mixed with water providing a moisture content of 5.0-10.0%, at which the maximum density and minimum porosity of the briquettes or binders are achieved, which can be sodium liquid glass, molasses, lemon balm or technical lignosulfonates. These binders ensure the integrity of the briquette during further heating. Pressing the prepared mixture at a pressure of 50 to 300 MPa facilitates the desulfurization and zinc sublimation reactions at lower temperatures. At pressing pressures less than 50 MPa, zinc sublimation is not facilitated, and pressures above 300 MPa are technically difficult to implement. The pressed briquettes had the shape of a cylinder with a height of 15 mm and a diameter of 15 mm. At a pressing pressure of 50 MPa, the original briquettes had a compressive strength of 5.4 MPa, and at a pressing pressure of 300 MPa, the ultimate compressive strength was 16.5 MPa. After firing, all briquettes had a strength of about 20 MPa.

When checking the possibility of implementing the claimed invention, sludge from the production of synthetic fibers was used, located in the area of Balakovo, Saratov Region. The average chemical composition of the sludge in terms of oxides is shown in Table 1.

The phase composition of the sludge is shown in Table 2.

Since the sludge contains limestone, and its amount in relation to sulfide is close to 1, two compositions were prepared for firing: the first to obtain the minimum stoichiometric ratio in the raw mixture, equal to the declared as 1.1:1.0, the second to obtain in raw mixture of a significant excess of limestone 1.7:1.0. The calculation of the compositions was carried out according to the standard method. The compositions of raw mixes are given in table 3.

The raw mixture was prepared by mixing the components in a mixer with the addition of 2 wt. % water. The dosage of the components of the raw mixture was carried out in accordance with the data presented in table 3. The duration of mixing was 30 seconds. The resulting mixtures were briquetted at a pressure of 50 MPa. The briquettes were fired at temperatures of 1100, 1200 and 1300°C with an isothermal exposure of 30 minutes. Roasting was carried out in an electric furnace chamber high-temperature (laboratory) brand SKV 12/14-V. Since complex physicochemical processes occur during the decomposition of the sludge, accompanied by the transformation of the sulfide form of zinc into oxide, which can only be detected by analyzing the phase transformation, the fired samples were subjected to both qualitative and quantitative phase analysis.

The qualitative phase composition of the sludge was determined by X-ray phase analysis (XPA) on a DRON-1 apparatus, the quantitative phase composition - on a STADi-P diffractometer (STORE, Germany), the chemical composition of the sludge was determined by X-ray fluorescence on an S4 Explorer spectrometer (Bruker AXS GmbH, Germany). ), thermogravimetric studies were carried out on a scanning calorimeter STA 449 F3 Jupiter (Netzsch-Geratebau GmbH) according to DIN 51004:1994.

Table 4 shows the phase composition of the sample at a ratio of 1.1:1.0, calcined at a temperature of 1100°C.

Table 5 shows the phase composition of the sample at a ratio of 1.1:1.0, calcined at a temperature of 1200°C.

Table 6 shows the phase composition of the sample at a ratio of 1.1:1.0, calcined at a temperature of 1300°C.

Table 7 shows the phase composition of the sample at a ratio of 1.7:1.0.

Table 8 shows the phase composition of the sample at a ratio of 1.7:1.0 calcined at a temperature of 1200°C.

Table 9 shows the phase composition of the sample at a ratio of 1.7:1.0, calcined at a temperature of 1300°C.

Table 10 summarizes the results of the content of zinc phases at realized firing temperatures in the sample at a ratio of 1.1:1.0.

Figure 1 shows the dependence of the change in the content of zinc phases in the sample by a ratio of 1.1:1.0 depending on the firing temperature.

Table 11 summarizes the results of the content of zinc phases at realized firing temperatures in the sample at a ratio of 1.7:1.0.

Figure 2 shows the dependence of the change in the content of zinc phases in the sample by a ratio of 1.7:1.0 depending on the firing temperature.

Since, at the realized firing temperatures, zinc is not completely removed from the samples, samples for a ratio of 1.1:1.0 and a ratio of 1.7:1.0 were heated to a temperature of 1350°C with an isothermal exposure of 30 minutes.

Table 12 shows the phase composition of the sample at a ratio of 1.1:1.0, calcined at a temperature of 1350°C with isothermal exposure.

Table 13 shows the phase composition of the sample at a ratio of 1.7:1.0, calcined at a temperature of 1350°C with an isothermal exposure of 30 minutes.

The results of firing confirm the possibility of implementing the proposed invention. As the firing temperature rises, zinc sulfide is converted to zinc oxide, which is reduced by carbon and sublimes. The decrease in the content of zinc sulfide and the increase in the content of zinc oxide with increasing firing temperature are clearly seen in Figures 1 and 2.

The firing results also indicate that when heated to a temperature of 1300°C without isothermal exposure, not all zinc is sublimated. In a sample for a ratio of 1.1:1.0, the residual content of zinc phases is 24.5%, and in a sample for a ratio of 1.7:1.0 - 15.0%. Increasing the firing temperature to 1350°C with an isothermal hold of 30 minutes makes it possible to completely remove zinc oxide.

Similarly, firing of briquettes with magnesite and dolomite was carried out at ratios less than the declared - 0.75:1.0 and more than the declared 1.25:1.0. The firing was carried out at a temperature of 1350°C. The firing results showed that at a ratio less than the stated 0.75:1.0, the residual content of zinc sulfide in the fired briquettes with magnesite was 28.0%, and in the fired briquettes with dolomite 17.8%. In briquettes with a ratio of more than the declared 1.25:1.0 with both magnesite and dolomite, zinc was not detected after firing.

Claims (6)

1. A method for processing zinc-containing materials, including preparing an initial mixture of a zinc-containing material, a solid carbonaceous reducing agent and a carbonate-containing flux, agglomeration of the resulting mixture by pressing, agglomeration of the agglomerated mixture, characterized in that the carbonate-containing flux is introduced into the initial mixture in an amount of (0.9-1 ,7):1 to the mass of zinc-containing material, the resulting mixture is subjected to homogenization by joint grinding to a specific surface area of the components from 3000 cm ² /g to 5500 cm ² /g, pressing is carried out at a pressing pressure of 50 MPa to 300 MPa, and the wafer is carried out at temperature 1100-1350°C. 2. The method according to p. 1, characterized in that dust and sludge from aspiration of industrial production are used as a zinc-containing material. 3. The method according to p. 1, characterized in that the solid carbonaceous reducing agent is introduced into the initial mixture in an amount of (0.1-0.3):1 by weight of the zinc-containing material. 4. The method according to p. 1, characterized in that, when used as a carbonate-containing flux, magnetite is introduced into the initial charge in an amount of (0.9-1.25): 1 by weight of the zinc-containing material. 5. The method according to claim 1, characterized in that when used as a carbonate-containing flux, dolomite is introduced into the initial mixture in an amount of (1.0-1.25):1 to the mass of the zinc-containing material. 6. The method according to claim 1, characterized in that when limestone is used as a carbonate-containing flux, it is introduced into the initial charge in an amount of (1.1-1.7): 1 by weight of the zinc-containing material.

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