RU2847160C1 - Zinc oxide production method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: zinc oxide production method involves feeding zinc-containing dust from electric arc furnaces, carbon-containing and slag-forming materials into a rotating quartz furnace while controlling their concentration and granulation. Anthracite is used as a carbon-containing material, and CaO is supplied to the slag formation zone of the Welz furnace in an amount that ensures a slag basicity of more than 1.5. The reduction of zinc oxide is carried out with the addition of anthracite controlled by concentration and granulation to ensure complete combustion of carbon in it in one processing cycle and rotation of the Welz furnace at a frequency of 0.8-1.2 rpm.

EFFECT: The production of lead oxide in one processing cycle in a lead furnace is ensured by regulating the process in each zone in the lead furnace by changing the concentration and granulation of anthracite and slag-forming material.

3 cl, 1 dwg, 1 tbl

Description

Field of technology

The invention relates to metallurgical technologies, in particular to the processing of zinc-containing dust from electric arc furnaces using the rolling method.

Prior art

Known is the patent RU 2340403 C2 from 20.06.2007 "Method for processing zinc-containing dusts and sludges from metallurgical and mining production", where the processing of sludge in ash sludge collectors and their processing is carried out by disintegration of the initial raw material in a continuous rotary-pulsation-cavitation apparatus at a solid-to-liquid ratio of 1:4 and at an excess pressure of 5 atmospheres at the entrance to the apparatus and further feeding the material into a flotation machine with the separation of zinc as a harmful impurity in the foam product and the chamber product sent for gravity classification, during which the separation of fine and coarse fractions is carried out, sent separately for wet magnetic separation in separators with permanent magnets with the production of a concentrated iron-containing concentrate, purified from zinc and tailings.

The disadvantage of this method is that there is no technology for further extraction of zinc from the foam product.

Known is patent RU 2588218 C2 "Method for hydrometallurgical processing of zinc-containing dusts from metallurgical production", where the processing of zinc-containing dust is carried out by leaching with a solution of sulfuric acid with the dissolution of compounds of non-ferrous metals in the form of sulfates, separation of the iron-containing precipitate to obtain a solution containing non-ferrous metals, characterized in that the leaching is carried out in autoclave conditions, at a temperature of 140 to 200 ° C, with a concentration of sulfuric acid from 220 to 250 g / l and a holding time of 2 hours, ensuring the extraction of zinc and cadmium into the solution up to 95-98%.

The disadvantage of this technology is its impracticality for industrial-scale use from primary raw materials (metallurgical dust), due to the need to use significant volumes of sulfuric acid as a consumable and to meet all the requirements for its storage, transportation, and operation.

The author's certificate SU 789619 from 23.12.1980 "Method for processing zinc-containing dusts from blast furnace and steelmaking production" is known, where in order to simplify the production of metallic iron and eliminate its contamination with sulfur, the reduction is carried out on the surface of the iron-carbon melt with weight ratios of zinc to sulfur in dusts in the range of (2-20):1, dust to iron-carbon melt in the range of (0.01-0.1):1 and the melt is blown with gas for 1-5 minutes.

The disadvantage of this method is that it does not provide for the extraction of zinc from zinc-containing dust.

Known is patent RU 2653394 C1 "Method for processing zinc-containing dust from electric arc furnaces", where the operations of mixing, pelletizing, Waelz-forming, and hydrometallurgical processing of zinc-containing clinker are distinguished in that the dust from electric arc furnaces is mixed before pelletizing with a material containing calcium oxide in an amount that provides the addition of calcium oxide in an amount of 70-110% of the content of iron oxide (Fe ₂ O ₃ ) in the dust, which is part of zinc ferrite (ZnO×Fe ₂ O ₃ ), and coke in an amount of 1-2% by weight of the said dust.

The disadvantage of this invention is that the introduction of calcium oxide in a volume of 70-110% of the content of iron oxide (Fe ₂ O ₃ ) in the dust will result in a basicity that is insufficient for the required reduction of the liquid phase.

The author's certificate SU 831833 "Method for processing zinc-containing dusts and sublimates" is known, where roasting is carried out together with sulfur-containing materials and subsequent leaching with sulfuric acid solutions, and in order to reduce the concentration of fluorine and chlorine in the cinder and reduce the process temperature, roasting of Waelz oxides is carried out with a consumption of sulfide material of 5-15% of the weight of Waelz oxides in the presence of water vapor at a blast temperature of 500-600 °C.

The disadvantage of this method is that it does not cover the process of obtaining the Waelz oxide itself, but only its subsequent calcination, and that the use of superheated steam at the specified temperatures leads to corrosion at the chemical level, which significantly reduces the service life of the Waelz kiln elements.

Patent WO 9804755 A1⋅1998-02-05 "Waelz Furnace Process for the Production of Zinc-Containing Materials" is known, where a charge is produced from zinc-containing material, a powdered solid fuel component, and an activator in a ratio of 8-12:2.5-7:0.8-1.5. The charge is mixed and granulated. The produced pellets, 1-30 mm in diameter and 16-18% moisture content, and the remaining solid fuel required for the process, are dosed according to a specified process mode, in a ratio of 3:1, and fed to the Waelz furnace. Oxygen in an amount of 3-12 ^m3 /t of processed charge is blown into the discharge end of the furnaces. Gases exiting the furnaces, containing non-ferrous metals, are cooled and undergo two-stage filtration in filtering equipment. The dust load in the exhaust gases after the first stage is up to 350 mg/ ^Nm³ , and after the second stage, it is below 10 mg/Nm³. The metal oxides collected in the filters are granulated into granules with a diameter of 2-6 mm and a moisture content of 13.6-16% and then sent for heat treatment in a tubular furnace, at the outlet of which oxygen is blown in an amount of 5-12 ^m³ /t of oxides. The resulting calcined metal oxides undergo further hydrometallurgical processing, the furnace gases are cooled, passed through filtration equipment, and the collected metal oxides are sent for additional cleaning and recovery, where the exhaust gases contain 4-8 mg/ ^Nm³ of dust.

The disadvantage of this method is that this technology requires additional cleaning equipment with two independent processing cycles.

According to the description in the source Matkarimov S.T. Technology of processing dusts of steelmaking production / S.T. Matkarimov, B.R. Ugli Karimdzhonov, M.S. Ergasheva, Z.S. Khmad Kizi Nazarova // Intellectual capital of the XXI century. - No. 11-6 (92) - 2021. - P. 26-28, where the process of iron reduction from oxides proceeds stepwise according to the following scheme: at temperatures above 560 ° C Fe ₂ O ₃ → Fe ₃ O ₄ → FeO → Fe, below 560 ° C magnetite is reduced to metallic iron, bypassing wustite Fe ₂ O ₃ → Fe ₃ O ₄ → Fe.

The disadvantage of this method is the lack of extraction of heavy metals from zinc, as well as the formation of high-pressure zinc vapor, which does not exclude their release into the atmosphere. Also, brown Angren coal was used as a reducing agent, due to the low carbon concentration in which it is difficult to regulate the complete process of reduction and complete combustion of carbon.

The prototype (the closest analogue) for the proposed invention is Japanese patent JP 2002241850 A, where the removal of zinc from zinc-containing iron oxide is carried out using a rotary furnace, by means of which the formation of a ring is prevented and the solid reduction of iron oxide is performed by separating zinc from zinc-containing iron oxide in a shorter time than in the conventional method, and the productivity can be improved. In the method for removing zinc from zinc-containing iron oxide using a rotary furnace 12, by means of which zinc-containing iron oxide is heated in a furnace 24 of the rotary furnace 12 and zinc is separated from the zinc-containing iron oxide and then the iron oxide is reduced to obtain an iron-containing material 25, a mixture of raw materials 11, consisting essentially of zinc-containing iron oxide and a carbonaceous material for the reduction of zinc oxide in zinc-containing iron oxide and iron oxide. The mixture of raw materials 11 is loaded into the furnace 24 of the rotary furnace 12, which has an air temperature of ≥1100°C in the furnace and zinc oxide in the zinc-containing iron oxide is reduced with a carbonaceous material and then evaporated to obtain iron-containing material 25, which is loaded into the reduction furnace.

The disadvantage of this invention is that zinc oxide is evaporated before drying, and during the evaporation process, heavy metals may also be present in the furnace gas, which makes their subsequent extraction difficult.

Disclosure of invention

The technical result to which the proposed invention is directed is: obtaining a product (Welz oxide) in one processing cycle in a Waelz kiln, as well as the possibility of regulating the process in each zone by changing the concentration and granulation of carbon-containing products and slag-forming mixtures.

The present invention relates to a method for producing zinc oxide, which includes feeding zinc-containing dust from electric arc furnaces, as well as carbon-containing and slag-forming materials, into a rotary Waelz kiln while controlling their concentration and granulation, characterized in that anthracite is used as the carbon-containing material, and the process of reducing zinc oxide in the Waelz kiln is carried out with the addition of anthracite, controlled by concentration and granulation, ensuring complete combustion of carbon in the anthracite in one processing cycle in the Waelz kiln and rotation of the Waelz kiln at a frequency of 0.8-1.2 rpm, while CaO is fed as a slag-forming material into the slag formation zone of the Waelz kiln in an amount that ensures the basicity of the slag formed in this zone, which is greater than 1.5, and the Waelz oxide obtained in the rotary Waelz kiln has the following composition, %:

zinc 40-60

lead 3-9

calcium 1-5

silicon 0.1-1.5

iron 0.1-3

sulfur 0.1-2

cadmium 0.1-1

manganese 0.1-5

potassium 0.1-2

sodium 0.1-2

chlorine 3-8

fluorine 0.1-0.5

oxygen is the rest.

In some embodiments of the method according to the present invention, in order to regulate the basicity of the slag, MgO is added in addition to CaO, wherein (CaO + MgO) / SiO ₂ > 1.5.

In some embodiments of the method according to the present invention, the obtained Waelz oxide is calcined in a quenching furnace to obtain a concentrate of the following composition, %:

zinc 55-70

lead 0.5-1.5

calcium 1-5

silicon 0.1-1.5

iron 0.1-3

sulfur 0.1-2

cadmium 0.1-1

manganese 0.1-3

potassium 0.1-2

sodium 0.1-2

chlorine 0.1-0.3

fluorine 0.1-0.3

oxygen is the rest.

Brief description of the drawings

The essence of the invention is explained by the drawing, where:

- in FIG. 1 Waelz kiln zones;

Implementation of the invention

The technical result is achieved due to the fact that the rotary Waelz kiln has 5 zones (FIG. 1):

1. Drying zone, where moisture and partially crystallized water are removed from the granulated Waelz oxide (zone temperature 750-850°C).

H ₂ O(l) ↔ H ₂ O(g)

2. Preheating zone, where an endothermic reaction with semi-combustion of anthracite occurs, while in the furnace atmosphere due to the reaction, thermal energy is generated (the temperature of the furnace zone is 850-1000°C).

CO + ¹ / ₂ O ₂ ↔ CO ₂ + Q

3. Pre-reaction zone, where volatile oxides evaporate and some stable iron oxides begin to be reduced (furnace zone temperature 1000-1300°C).

CdO + CO ↔ Cd + CO ₂

CuO + CO ↔ Cu + CO ₂

Fe ₂ O ₃ + CO ↔ 2 FeO + CO ₂

Fe ₃ O ₄ + CO ↔ 3 FeO + CO ₂

C + CO ₂ ↔ 2 CO

CO + ¹ / ₂ O ₂ ↔ CO ₂ + Q

4. The main reaction zone, where zinc and lead oxide are reduced to metallic zinc and lead. The remaining iron oxides, in the form of wustite (FeO - Fe _0.83 O), are reduced to metallic iron (the furnace zone temperature is about 1200°C).

ZnO + CO ↔ Zn + CO ₂

PbO + CO ↔ Pb + CO ₂

FeO + CO ↔ Fe+CO ₂

C + CO2(g) ↔ 2 CO(g)

ZnO⋅Fe ₂ O ₃ + CO ↔ 2 FeO + ZnO + CO ₂

ZnO⋅SiO ₂ + CO ↔ Zn + SiO ₂ + CO ₂

To re-oxidize the metallic lead, zinc, and iron condensed in the furnace atmosphere, air is blown from the furnace head onto the solid Waelz slag by means of an oxidation lance.

Zn + ¹ / ₂ O ₂ (g) ↔ ZnO

Pb + ¹ / ₂ O ₂ ↔ PbO

CO + ¹ / ₂ O ₂ ↔ CO ₂ +Q\

Metallic lead and zinc oxidize and condense as a cloud of lead oxide and zinc oxide dust in the furnace atmosphere and return to dust.

For further cooling and solidification, water is sprayed in (the temperature drops to 300-350°C). The gas is then cooled to 150°C in the outlet heat exchanger and collected in a filter as Waelz oxide.

Heavy metals such as dioxin, furan, mercury, micropollutants and gases Cl, SO _X in the exhaust gases, passing through the activated carbon reactor and the second filter for absorption, are filtered and not released into the atmosphere, where clean air is released.

5. The slag formation zone, where the reduced iron in the main reaction zone combines with oxygen from the oxidation lance, reverting to iron oxide and mixing with the slag. Air supplied from the oxidation lance minimizes the temperature generated during anthracite combustion, causing the slag to leave the furnace at 900-800°C. To increase the slag basicity, quicklime is added at a ratio of (CaO + MgO) / _SiO2 > 1.5.

To optimize the operation of the furnace and ensure complete reduction (complete combustion of carbon in anthracite), a rotation speed of n=0.8-1.2 rpm is used.

Also, after the entire process has been completed, it is possible to additionally calcinate the Waelz oxide to obtain a concentrate with a higher content of pure zinc due to the removal of lead and chlorine.

Thus, the technical result is achieved, which consists in obtaining Waelz oxide in one processing cycle in a Waelz kiln, with an optimal operating mode in terms of temperature-time parameters, allowing both controlled reduction with complete combustion of carbon and obtaining optimal slag fluidity, due to controlled basicity with the addition of CaO + MgO.

The use of the proposed technology will allow:

- By controlling the furnace temperature, concentration flow rate and granulation of anthracite, create the most efficient reduction process in the furnace, with complete combustion of carbon.

By optimizing the furnace rotation, create coordination between the furnace operating modes in the furnace zones.

By controlled supply of lime, control the basicity and fluidity of slag for its complete removal.

By using controlled temperature and time parameters, maximum productivity can be achieved during the entire process.

Claims (5)

1. A method for producing zinc oxide, which includes feeding zinc-containing dust from electric arc furnaces, as well as carbon-containing and slag-forming materials, into a rotary Waelz kiln while controlling their concentration and granulation, characterized in that anthracite is used as the carbon-containing material, and the process of reducing zinc oxide in the Waelz kiln is carried out with the addition of anthracite, controlled by concentration and granulation, ensuring complete combustion of carbon in the anthracite in one processing cycle in the Waelz kiln and rotating the Waelz kiln at a frequency of 0.8-1.2 rpm, while CaO is fed as a slag-forming material into the slag formation zone of the Waelz kiln in an amount that ensures the basicity of the slag formed in this zone, which is greater than 1.5, and the Waelz oxide obtained in the rotary Waelz kiln has the following composition, %: zinc 40-60 lead 3-9 calcium 1-5 silicon 0.1-1.5 iron 0.1-3 sulfur 0.1-2 cadmium 0.1-1 manganese 0.1-5 potassium 0.1-2 sodium 0.1-2 chlorine 3-8 fluorine 0.1-0.5 oxygen the rest 2. The method according to paragraph 1, characterized in that, in order to regulate the basicity of the slag, MgO is added in addition to CaO, wherein (CaO+MgO)/ _SiO2 >1.5. 3. The method according to paragraph 1, characterized in that the obtained Waelz oxide is subjected to calcination in a hardening furnace to obtain a concentrate of the following composition, %: zinc 55-70 lead 0.5-1.5 calcium 1-5 silicon 0.1-1.5 iron 0.1-3 sulfur 0.1-2 cadmium 0.1-1 manganese 0.1-3 potassium 0.1-2 sodium 0.1-2 chlorine 0.1-0.3 fluorine 0.1-0.3 oxygen rest