RU2280087C2 - Method for continuous processing of iron and zinc containing dusts and alloys - Google Patents

Abstract

FIELD: ferrous metallurgy, possibly processing of iron and zinc containing materials being waste products, for example dusts and alloys of gas scrubbers of open hearth and blast furnaces, of converters.

SUBSTANCE: method comprises reduction annealing at presence of reducing agent in rotary tubular furnace without air access in controlled-temperature mode for producing metal plated iron-containing product and zinc product. Mixture of initial material and reducing agent is preliminarily processed at temperature no less than 400°C till humidity content no more than 0.05% and then such mixture is fed into rotary tubular furnace. Reduction annealing in such furnace is realized due to contact free heating with use of heat exchanger mounted in said furnace due to supplying combustion products into said heat exchanger. Zinc condensate is trapped and cooled for producing zinc product in the form of metallic zinc.

EFFECT: possibility for producing zinc product in the form of metallic zinc at lowered consumption of reducing agent.

2 cl, 1 tbl

Description

The invention relates to the field of ferrous metallurgy and can be used for the processing of iron-zinc-containing materials, which are waste products, for example, dust and sludge from gas-treatment open-hearth furnaces and blast furnaces, as well as converters.

A known method and installation for removing zinc from materials containing iron oxides (Japanese application No. 61-12979 C 22 V 19/06, C 21 V 13/02, F 27 V 1/08, 5/00, published 86.04.11 No. 3-325). According to this method, agglomerated iron-containing material with a minimum particle size of 5 mm, containing zinc oxides, is loaded in a mixture with a reducing agent in a vertical muffle furnace. The technological mode of firing is selected so that the reduction of Fe ₂ O ₃ and Fe ₃ O _{4 is} carried out to FeO at temperatures of 650-900 ° C. The resulting zinc vapor is removed along with the gas. The disadvantages of this method are: the need for agglomeration of iron-zinc materials, the inefficiency of heating the charge, the restoration of higher iron oxides only to FeO, zinc oxides are not captured.

According to the author’s certificate (USSR AS No. 789619 C 22 B 7/02 published in BI No. 47 for 1980), a method for processing zinc-containing dusts from blast furnace and steelmaking by supplying agglomerated material (briquettes are made from dusts and sludges) is proposed the surface of the iron-carbon melt or blowing dust with a carrier gas into the mass of the melt. Dust or briquette is melted due to the heat of a large mass of iron-carbon melt, on the surface of which the process of reduction of iron and zinc oxides takes place. During the recovery period, the iron-carbon melt is purged with a gas, such as air or nitrogen, for 1-5 minutes to remove sulfur dioxide and zinc metal vapor. The disadvantages of this method: the need to combine the proposed technology with the current production - the Converter, which is organizationally difficult; when blowing dust, an additional installation is required, and when working with a briquette, a briquette press, an additional blowing of the melt, leads to a significant burnup of dissolved carbon and oxidation of iron.

A known method of industrial distillation (recovery) of zinc from concentrates containing 50-55% or more Zn (F.M. Loskutov. Metallurgy of heavy non-ferrous metals. Part II. Lead and zinc. GNTI literature on ferrous and non-ferrous metallurgy, M., 1951 , pp. 266-288). The zinc-containing concentrate, which has previously undergone thermal firing, mixed with a reducing fuel, which uses coal, metallurgical coke, is loaded into a stationary retort, which is heated from the outside. The technological temperature of the charge heating is 1000 ° C and above. As a result of the recovery, zinc vapors enter the condenser, in which they are deposited in the form of liquid metal, and the non-condensed part of the zinc vapors is trapped in the alloy in the form of zinc dust. The disadvantages of this method: low productivity due to imperfections in the process, namely, unsatisfactory heat and mass transfer of the fixed layer of the charge in the retort, high fuel consumption and the amount of manual work.

The closest in technical essence is a method of processing blast furnace and steel sludge, including reducing firing, carried out with the addition of a solid reducing agent at a temperature in the range of 950-1100 ° C, in a rotary kiln to obtain an iron-containing product and a zinc product, which is then captured (US patent 4213778 Cl. 21B 3/04, publ. 07/22/1980).

The disadvantages of the prototype are the following:

- zinc-containing waste with a moisture content of 35-55% is subjected to heat treatment, which does not allow to obtain a zinc product in the form of metallic zinc due to the oxidation of zinc vapor by water vapor;

- the process of heat treatment of waste in a rotary kiln is carried out in an oxidizing atmosphere so that partially reduced iron oxides are stored in the processed material due to the presence of carbon in it, and the evaporating zinc is converted into zinc oxide and removed from the furnace by gas counterflow, which does not allow to obtain a zinc product in the form of zinc metal due to the oxidation of zinc vapor by oxygen in the blast and carbon dioxide formed during the oxidation of carbon;

- the heat necessary for the implementation of the processes of reduction of iron and zinc oxides, as well as the evaporation of metallic zinc, is obtained in the working space of a rotary kiln during the oxidation of carbon, zinc vapors, and additionally when burning fuel by supplying air blast, which does not allow to obtain a zinc product in the form zinc metal due to the oxidation of zinc vapor by oxygen in the blast, water vapor and carbon dioxide formed during the combustion of fuel with excess air;

- the amount of coke introduced into the firing mixture as a carbon reducing agent is 10-15%, which together with the waste carbon is 1.5-2 times higher than the stoichiometrically necessary for partial reduction of iron and zinc oxides, which leads to an increased consumption of reducing agent and the need separation of the iron-containing product.

The technical result of the invention is to obtain a zinc product in the form of metallic zinc and reducing the consumption of reducing agent.

The specified technical result is achieved by the fact that in the method for the continuous processing of iron-zinc dusts and sludges, which includes reducing firing in the presence of a reducing agent in a rotary tube furnace without air access at a controlled temperature regime to obtain a metallized iron-containing product and a zinc product, according to the invention, the mixture of the starting material and reducing agent is preliminarily treated to a moisture content of not more than 0.05%, after which it is fed into the said furnace, a reducing agent in which firing is carried out by non-contact heating by a heat exchanger installed in the furnace by supplying fuel combustion products to it, and zinc condensate is obtained, which is captured and cooled to obtain the zinc product in the form of metallic zinc. In this case, pre-treatment is carried out at a temperature of at least 400 ° C.

The implementation of the method in the present invention is provided as follows: iron-zinc-containing materials - dust and sludge from gas purification of metallurgical plants mixed with a certain amount of a reducing agent (coal or metal coke) in the case of obtaining metal zinc undergo a drying operation, for example, in a drying drum. The starting materials must not contain moisture before firing and reduction in order to avoid oxidation of zinc vapors. The dried material is loaded with a screw feeder into a rotary kiln having an adjustable speed of rotation and angle of inclination. Flue gases with an appropriate temperature pass through a heat exchanger mounted inside the furnace. The temperature of the material in the furnace is maintained within 950-1100 ° C. The material falling into the furnace moves during its rotation, which contributes to a more perfect heat transfer and accelerate the recovery of zinc and iron oxides compared to the prototype. The resulting zinc vapor through a discharge steam line enters the condenser, is cooled and flows into the reservoir tank. As for iron oxides, they are reduced at given temperatures and as a result, a metallized iron-containing product is obtained, which is discharged into a receiving hopper, where it is cooled without access of air. Further, this material is subjected to magnetic separation and the resulting metallized concentrate can be used directly, or after briquetting as a commercial product for subsequent redistribution.

The products of combustion from the heat exchanger through the flue enter the waste heat boiler or to dry the source material.

In laboratory conditions, experiments were conducted on firing open-hearth dust of the Nizhne-Tagilsky metallurgical plant of the following chemical composition,%: Fe _total - 46.88; FeO — 0.26; Fe ₂ O ₃ 66.68; ZnO - 3.25. A portion of the charge (a mixture of dust and coke) was loaded into an alundum container, which was connected to a condenser through a ceramic stopper. During firing, the container together with the capacitor was turned after a certain period of time. The degree of metallization and zinc removal was calculated according to chemical analysis. The results of the experiments are shown in the table.

The sequence of operations in the proposed method: a continuous process with an adjustable speed of movement of the material, non-contact heating with gases, an adjustable temperature regime allows to obtain metallic zinc, and, if necessary, zinc oxide, as well as metallized, from iron-zinc-containing materials - dusts and sludge from metallurgical industries iron-containing product that allows you to reuse them. The main indicators of the process are the almost complete removal of zinc oxides (the degree of removal is more than 98%). The proposed method is environmentally friendly, heat is almost completely used, technologically simpler than the prototype.

Table
The effect of temperature and holding time on the degree of metallization and zinc removal Experience number Firing temperature, ° С Firing time, h The degree of metallization,% The degree of removal of zinc,% one 950 0.5 38.7 39.6 2 950 1,0 50.8 49.9 3 1050 0.5 65.5 69.5 four 1050 2.0 89.3 93,4 5 1100 1,5 94.7 96.0 6 1100 2.0 96.7 98.9

Claims (2)

1. A method for the continuous processing of iron-zinc dusts and sludges, including reducing firing in the presence of a reducing agent in a rotary tube furnace without air access at a controlled temperature regime to obtain a metallized iron-containing product and zinc product, characterized in that the mixture of the starting material and the reducing agent are pre-treated to moisture content not more than 0.05%, after which it is fed into the aforementioned furnace, the regenerative firing in which is carried out by After heating by a heat exchanger installed in the furnace by feeding fuel combustion products into it, zinc condensate is obtained, which is captured and cooled to obtain the zinc product in the form of metallic zinc. 2. The method according to claim 1, characterized in that the pre-treatment is carried out at a temperature of at least 400 ° C.