RU2156314C1 - Method of water washing of zinc cakes - Google Patents

Abstract

FIELD: zinc metallurgical production, particularly, washing of industrial products of zinc production, for instance zinc cakes. SUBSTANCE: into pulp of zinc cake is water containing butyl xanthate. Consumption of butyl xanthate amounts up to (2.5-3.0)•10^-2% of zinc cake weight. Components are mixed by mechanical mixing and aeration to obtain zinc cake with content of sulfur of 1.1 -1.4% including sulfate sulfur of 0.9-1.1% and sulfide sulfur of 0.2-0.3%. EFFECT: increased technical-and-economic indices of rotary-kiln processing of zinc cake, reduced content of sulfur in effluent gases from 0.022 to less than 0.01%. 1 tbl, 1 ex

Description

 The invention relates to the field of metallurgical production of zinc, in particular the washing of industrial products of zinc production, for example zinc cakes.

 A known method of water washing industrial products of zinc production, for example zinc cakes, including filtering cake on a frame vacuum filters, blowing it (discharge) into a washing hopper, mixing with compressed air and subsequent filtering on disk vacuum filters (AP Snurnikov. Zinc hydrometallurgy. . - M., 1981 p. 153).

 The disadvantage of this method is the low degree of separation of sulfur-containing zinc compounds (sulfates, sulfides), the high residual sulfur content in the cake, which complicates its further processing, for example in Waelz furnaces.

 The closest to the invention in technical essence and the achieved result (prototype) is a method of countercurrent washing of zinc cakes, including countercurrent washing using water as a washing liquid with the addition of sulfuric acid as an auxiliary substance in an amount providing a pulp pH of 1-4, and implemented by countercurrent mixing in three successive reactors, ("Method for water washing pulp of zinc cakes" A.S. N 648631 from 05.24.77).

 The disadvantage of this method is the high residual sulfur content in the zinc cake in the form of zinc sulfides and sulfates, because of the low degree of sulfate washing, the residual sulfate sulfur content in the cake is 2-3%, and sulfide sulfur (1-2%) remains almost completely in the cake.

 Sulfate and sulfide sulfur complicates the further processing of cake. So at Waelz, the material melts, which leads to an increased consumption of coke and increases the loss of zinc with clinker.

A method is proposed for water washing zinc cakes using butyl xanthogenate as an auxiliary substance at a flow rate equal to (2.5 - 3.0) 10 ^-2 plumb zinc cakes, and subsequent mixing of the components, which is carried out by aeration and mechanical stirring.

 The proposed method is tested in an industrial environment. Tests have shown that this method allows you to almost completely wash zinc cake from sulfates, and remove sulfides in the form of "zinc concentrate." The zinc cake obtained after this treatment can be processed without complications in Waelz kilns.

 Information confirming the possibility of implementing the proposed method.

 Verification of the method of water washing zinc cake was carried out as follows.

Water was introduced into the pulp of zinc cake with a solid phase, 80-97% consisting of particles with a size of less than 60 microns, with a liquid phase (zinc content 80 - 150 g / l), flow rate 0.5-0.7 kg / t cake) containing butyl xanthate. The consumption of butyl xanthate is (2.5 - 3.0) 10 ^-2 % by weight of zinc cake. Next, the components were mixed by aeration and mechanical stirring.

 The dosage of butyl xanthate to the pulp of industrial products of zinc production, for example zinc cakes, allows intensifying the process of washing zinc sulphates with water, separating zinc sulphides from zinc cake and ensuring efficient processing of zinc cake in Waelz kilns. After washing the zinc cake, the “solution” passes through a thickener, where sulfides are precipitated in the form of a “zinc concentrate”, and then goes on to extract zinc. The "zinc concentrate" is returned to the firing or hydrometallurgical recovery of zinc and related metals.

 The table and example shows comparative data of the known method of washing (prototype) and the proposed.

 Example.

The pulp of zinc cake obtained after leaching of the cinder has the following characteristic:
solid content in the pulp 50-500 g / l;
pH 4.5-5.1;
composition of the solid phase,%: zinc - 19-22; total sulfur - 5.5-6.5; sulfate sulfur - 4.5-5.1; sulfide sulfur - 0.8-1.3; iron - 25-30; copper - 2.6-2.8; lead - 1.5-2.5; silver - 0.025-0.044. Zinc is associated with sulfur sulfate, sulfide, as well as in the form of ferrites and partially silicates.

solid phase sieve characteristic:
class, micron +100 +50 -50
class yield,% 0.7 1.2 98.1.

An aqueous solution of potassium butyl xanthate with a concentration of 1-2% was calculated into the pulp after leaching, so that its consumption was [2.2; 2.5; 2.7; 3.0; 3.2] • 10 ^-2 by weight of zinc cake. Then the pulp was sent to the reactor, where it was mixed with compressed air. The "solution" together with particles ("zinc concentrate") was constantly merged through the side hole in the upper part of the reactor and sent to sedimentation and subsequent filtration. Washed zinc cake in the form of pulp with w: t = 2: 1 through the hole in the lower part of the reactor was sent to thickening and filtering on disk vacuum filters. The filtered cake was dried and processed in a Waelz kiln.

At the same time, zinc cake was obtained with a sulfide sulfur content of 0.2-0.3%, sulfate sulfur 0.9-1.1%. The filtration rate of zinc cake was 1.2-1.3 t / m ³ days. Processing of cake in Waelz kilns proceeded stably, the formation of melts ("baths") was not observed, the consumption of coke breeze amounted to 350 kg / t cake, zinc content in clinker was 0.4%, and sulfur dioxide in the exhaust gases of Waelz kilns was less than 0, 01%

 For comparison, the prototype experiment was carried out, while sulfuric acid was introduced into water in an amount providing a pH of zinc cake pulp equal to 3.5 as an auxiliary substance. The pulp was washed by countercurrent in three successive thickeners. The condensed product was filtered on disk vacuum filters, dried and processed in Waelz kilns. The obtained zinc cake contained: sulfide sulfur - 1.1-1.2%, sulfate sulfur - 2.5-2.6%. The filtration rate of this cake was 1.0-1.1 t / m day.

 During its subsequent Waelz process, the process proceeded unstable: the material was deposited with the formation of "baths", the coke consumption was 380 kg / t cake, and the zinc content in the clinker was 1.0-1.2%. In the exhaust gases of Waelz kilns emitted into the atmosphere, the content of sulfur dioxide was 0.027%. After washing zinc cakes with a solid content (about 3 g / l), the “solution” passes through a thickener, where the “zinc concentrate” is separated, and then goes to the main zinc production cycle to extract zinc. Zinc concentrate having a composition,%: zinc - 31-35; iron - 15-20; copper - 3.9-4.1; lead 2.5-3.0; sulfide sulfur - 13-15; sulfate sulfur - 0.5-0.6; silver - 0.2-0.4, sent to the head of the process for firing or involved in hydrometallurgical processing with the extraction of zinc and related components.

 Technological indicators of water washing of zinc cakes from sulfur-containing zinc compounds are given in the table.

As can be seen from the table, an increase in the consumption of butyl xanthate more than 3.0 • 10 ^{-2 is} impractical, because will not lead to a decrease in the sulfur content in zinc cake and to an increase in the Waelz index. Reducing the consumption of butyl xanthate below 2.2 • 10 ^-2 does not give a significant positive effect.

Thus, when used in the proposed method as an auxiliary substance, butyl xanthate, its optimal consumption is (2.5-3.0) • 10 ^-2 % of the weight of zinc cake.

Using the proposed method, in comparison with the known provides:
reduction of sulfur content in zinc cake:
sulfide from 1.1-1.2% to 0.2-0.3%
sulfate from 2.5-2.6% to 0.9-1.1%
improves Waelz performance
the zinc content in clinker is reduced from 1.2 to 0.4%;
the content of sulfur dioxide in the exhaust gases of Waelz kilns is reduced from 0.027 to <0.01%.

 it turns out a serocin-containing intermediate product - "zinc concentrate", suitable for the extraction of zinc and related metals.

Claims (1)

A method of water washing zinc cakes, comprising mixing by mechanical stirring and aerating the pulp of zinc cake with water containing an excipient, characterized in that butyl xanthate is used as an excipient at a flow rate of (2.5 - 3.0) • 10 ^-2 % by weight of zinc cake.

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