BG66863B1 - Method for recycling slag from copper production - Google Patents

Abstract

The method is applicable to obtain useful products from industrial waste from copper production, which solves the environmental problem related to the reduction of the quantity of waste products and the costs of their disposal. The fayalite contained in the slag is oxidized and decomposed to iron oxides and silicon dioxide at a temperature of 800 to 850° C and a duration of 3 to 5 hours. The oxidized slag is mixed with a solution of sodium hydroxide in water with a concentration of 30-90 g/l and is subjected to extraction in an autoclave at a temperature of 160 to 250oC, autogenous vapor pressure of water of 0.6 to 4 MPa, at continuous stirring and duration of the process 3-9 h, in which the silicon dioxide is dissolved in sodium hydroxide until a liquid phase reaction, containing sodium silicate. The liquid phase is separated and the solid phase of iron oxides is subjected to a secondary process in an autoclave by washing with water at a temperature of 150 to 250° C, autogenous vapor pressure of water of 0.6 to 4 MPa and at continuous stirring. The resulting suspension is subjected to vacuum filtration, as the solid phase is separated for pelleting, and the liquid phase, which is a solution of sodium silicate, is mixed with the reaction liquid phase from the first extraction and subjected to treatment by acidification with hydrochloric acid to release colloidal silicon hydroxide, which polymerizes and condenses to a gel. The resulting colloidal system is centrifuged, washed to remove soluble salts, and filtered to separate the gel, which is subjected to drying in order to obtain amorphous silicon dioxide (silica gel) with predetermined grain and surface sizes.

Description

Field of technology

The invention relates to a method for processing copper slag obtained in the production of copper by pyrometallurgical method.

BACKGROUND OF THE INVENTION

In the production of copper by pyrometallurgical method, pyrite is oxidized to iron oxide, which in the presence of silicon dioxide forms fayalite (Fe ₂ SiO ₄ ), the main component of the slag. The slag is usually deposited directly in slag storage or used for road ballast, embankments, sandblasting material, iron-containing cement additive or tile material. Efforts for slag processing are mainly focused on the extraction of precious metals such as copper and zinc, where the amount is not significantly reduced.

US 4,001,011 A describes a pyrometallurgical method for extracting the iron phase from copper slag. It is kept at high temperatures 1400-1500 ° С. No reagents are used, but a carbon (reducer) - coke. The aim is not to completely recycle the slag, but only part of the iron. The silicon fraction is a new slag that is disposed of as waste.

DE 199 46 326 A1 discloses a method for recycling slag-containing felite, which comprises treating the granulated slag with sulfuric acid, oxidizing the iron compounds in the slag at a temperature of 550 to 750 ° C for 1 to 4 hours, filtering slag at room temperature and dissolution of non-ferrous metal compounds - Zn, Cu.

The described processes do not provide extraction of iron oxides and silicon dioxide from the slag.

EP 2 331 717 B1 discloses a method for recycling copper slag containing iron silicate fayalite, in which fayalite is oxidized in air at a temperature of 700-1100 ° C and a duration of 3 to 5 hours to obtain a mixture of magnetite, hematite and quartz. The mixture is treated with an alkali metal hydroxide or carbonate to give a mixture of alkali metal silicate and iron oxides, which is mixed with water and heated at atmospheric pressure to a temperature of 100 ° C or at a pressure of 0.6 to 1.5 MPa and a temperature of 150- 250 ° C, in which the silicate passes into an aqueous solution in the form of an alkali metal silicate and / or a solution of silicon in an alkali metal hydroxide, and the undissolved iron oxides are separated by precipitation or filtration and washed with aqueous saline or sulfur. acid with a concentration of up to 0.25M. The result is an iron concentrate and alkali metal silicate and / or a solution of silicon in alkali metal hydroxide, which can be used for the production of water glass, without describing the processes for obtaining the final useful products iron oxides and amorphous silicon. dioxide.

Each of the described known methods does not significantly reduce the amount of waste products, which creates a condition for environmental pollution.

Technical essence of the invention

The aim of the invention is to provide a method for processing copper slag to useful products - iron pellets and amorphous silica - silica gel, which solves an environmental problem associated with a significant reduction in the amount of waste products and the cost of their disposal.

The method for processing copper slag containing iron silicate - fayalite, involves oxidation of fayalite in air, its decomposition to a mixture of iron oxides and silicon dioxide and treatment of the resulting mixture with sodium hydroxide solution. According to the invention, the slag fayalite is oxidized and decomposed to iron oxides and silica at a temperature of 800 to 850 ° C and a duration of 3 to 5 hours. The oxidized slag is mixed with a solution of sodium hydroxide in water with a concentration of 30-90 g / Ι and subjected to extraction in an autoclave at a temperature of 160 to 250 ° C, autogenous water vapor pressure of 0.6 to 4 MPa, with constant stirring and the duration of the process is 3-9 hours, during which the silica is dissolved in sodium hydroxide to give a reaction liquid phase containing sodium silicate. The liquid phase is separated and the solid phase of iron oxides is re-extracted in an autoclave by washing with water at a temperature of 150

Descriptions of issued patents for inventions № 05.1 / 15.05.2019 up to 250 ° С, autogenous water vapor pressure from 0.6 to 4 MPa and with continuous stirring. The resulting suspension is subjected to vacuum filtration, the solid phase of iron oxides is separated for pelleting, and the liquid phase, which is a solution of sodium silicate, is mixed with the reaction liquid phase from the first extraction and treated by acidification with hydrochloric acid until separation. of colloidal silicon hydroxide, which polymerizes and condenses to a gel. The resulting colloidal system was centrifuged, washed to remove soluble salts, and filtered to separate the gel, which was dried to obtain a fine, powdered amorphous silica (silica gel).

In one embodiment of the invention, the acidification is carried out with hydrochloric acid at room temperature until pH 2 is reached, wherein the process of saturating the solution and obtaining a gel is 12-24 hours.

In a second embodiment of the invention, the acidification is carried out with hydrochloric acid at a temperature in the range of 60 to 90 ° C until a pH of 6 is reached, wherein the process of saturating the solution and obtaining a gel is 6-12 hours.

Drying of the gel is carried out in an oven at 60-90 ° C for 24-48 hours or in a spray drying installation under vacuum and temperature 300-800 ° C to obtain silica gel with predetermined grain sizes and surface.

The advantages of the method according to the invention consist in obtaining useful products from industrial waste from copper production, which solves an environmental problem related to the reduction of the amount of waste products and the costs for their disposal. The quality of the obtained useful products - iron pellets and amorphous silica is high.

Explanation of the attached figure

Figure 1 is a flow chart for the processing of copper slag according to the invention.

Examples of the invention

The method for processing copper slag obtained in the pyrometallurgical production of copper includes the following steps (Fig. 1):

I. Screening

The slag is sieved with a 100 mesh sieve in order to remove larger, incidental inorganic and organic materials that may affect the oxidation process.

II. Thermal oxidation of slag

The sieved slag is oxidized in a furnace with varying technological parameters: oxidation temperature and oxidation time. The furnace unit can be: 1) stationary, with blowing with oxidizing gas in the mode of "boiling" or "pseudo-boiling" layer; 2) rotary kiln, without or with slag mixing.

The oxidation of fayalite in the slag is carried out in air with or without the addition of oxygen to the gas atmosphere at temperatures of 800-850 ° C and duration from 2 to 4 hours. Chemical reactions during oxidation:

2FeO.SiO ₂ + ¹ / zO ₂ ^ Fe ₂ O ₃ + SiO ₂ (1)

2FeO. SiO ₂ + 7z O ₂ - + Fe ₃ O ₄ + SiO ₂ (2)

Oxidized slag must not contain residual fayalite.

III. Cooling

The oxidized slag is cooled to room temperature, and the cooling can be carried out with the furnace, in a separate vessel or in air outside the furnace space.

IV. Mixing

The oxidized slag is mixed with an aqueous solution of sodium hydroxide in a ratio of slag - solution 1: 1 to 1: 3. The concentration of the solution is in the range of 30-90 g / l.

V. Extraction of the silicate phase under pressure

The stage is realized in an autoclave at temperatures of 160-25 0 ° С and the corresponding autogenous water vapor pressure; retention time at this temperature 3-9 h. As a result, the silicate phase reacts with

Descriptions of issued patents for inventions № 05.1 / 15.05.2019 sodium hydroxide and a solution of sodium silicate is obtained. As the process is carried out under pressure, after its end part of the solution is pumped into a series of tanks to reduce the pressure and temperature. The suspension is removed from the autoclave at a temperature below 100 ° C.

VI. Filter the suspension with a membrane filter.

VII. Separation of the solid phase containing iron oxides from the sodium silicate solution.

VIII. The solid phase is mixed with water in a ratio of 1: 1 to 1: 3.

IX. The solid phase is returned to the autoclave for re-extraction.

Due to the high viscosity of the sodium silicate solution, part of it envelops the grains of the solid phase. To completely recover the synthesized sodium silicate from the solid phase, it is washed with pressurized water. The process is carried out in an autoclave at temperatures of 150-250 ° C and the corresponding autogenous water vapor pressure. The retention time at this temperature is 1-3 h.

X. Filtration

The suspension of step VIII is filtered through a membrane filter.

XI. Separation of the solid phase from iron oxides from the liquid phase.

XII. Pelletizing of the solid phase from iron oxides.

XIII. Mixing of the liquid phases

The liquid phases of the first and second extraction are mixed.

XIV. Acidification and saturation of the solution and gel formation.

1). In one embodiment of the invention, the sodium silicate solution is acidified with hydrochloric acid at room temperature until pH 2 is reached, whereby the process of saturating the solution and obtaining a gel is 12-24 hours.

2) In a second embodiment of the invention, the sodium silicate solution is acidified with hydrochloric acid at a temperature in the range of 60 to 90 ° C until a pH of 6 is reached, whereby the process of saturating the solution and obtaining a gel is 6-12 h.

XV. Filtration

The suspension obtained in step XII was centrifuged, washed and filtered. The washing step is repeated until the soluble salts are removed from the gel.

XVI. The liquid phase (lye) obtained in step XIII is taken to a basin.

XVII. Drying of the gel.

The silica gel is dried at a temperature of 60-90 ° C for 24-48 hours or in a spray drying system under vacuum and at a temperature of 300-800 ° C, which produces amorphous silica (silica gel) with predetermined grain sizes and surface .

The invention is illustrated by the following specific examples, which do not limit it.

Example 1.

The oxidized slag is mixed with 60 g of NaOH and 1000 ml of water, placed in an autoclave and heated with continuous stirring to a temperature of 180 ° C, at which it is kept for 6 hours. At the end of the process, the solution is filtered. The liquid phase contains 21 g / l Si.

The solid residue is returned to the autoclave with 1000 ml of water and heated with continuous stirring to a temperature of 180 ° C at which it is kept for 2 hours. At the end of the process, the solution is filtered. The liquid phase contains 2.23 g / l Si.

The chemical composition of the solid residue in wt. % is:

FeO MgO CaO MnO SiO ₂ A1 ₂ O ₃ Na ₂ OK ₂ O TiO ₂

86.69 0.97 0.87 <0.01 6.163 3.04 1.92 <0.01 0.66

The liquid phases of the two filtrations are mixed. The mixture was acidified with hydrochloric acid at room temperature until pH 2 was reached. The process of saturation and gel formation was 12-24 hours. The suspension was centrifuged, washed and filtered to remove soluble salts. The washing step was repeated two more times, after which the gel was dried at 80 ° C for 24 hours.

The solutions after centrifugation and washing of the gel are mixed and separated as an alkali. The composition of the lye in wt. % e: Na ₂ O - 26.12; A1 ₂ O ₃ - 12.67; SiO ₂ - 4.17; Cl - 47.32; K ₂ O - 1.35; CaO - 4.18; FeO-3.11.

Descriptions of issued patents for inventions № 05.1 / 15.05.2019

Example 2.

The oxidized slag is mixed with 60 g of NaOH and 1000 ml of water, placed in an autoclave and heated with continuous stirring to a temperature of 180 ° C, at which it is kept for 6 hours. At the end of the process, the solution is filtered. The liquid phase contains 21 g / l Si.

The solid residue is returned to the autoclave with 1000 ml of water and heated with continuous stirring to a temperature of 180 ° C at which it is kept for 2 hours. At the end of the process, the solution is filtered. The liquid phase contains 2.23 g / l Si. The chemical composition of the solid residue in wt. % is:

FeO MgO CaO MnO SiO ₂ A1 ₂ O ₃ Na ₂ OK ₂ O TiO ₂

86.69 0.97 0.87 <0.01 6.163 3.04 1.92 <0.01 0.66

The liquid phases of the two filtrations are mixed. The mixture was acidified with hydrochloric acid at room temperature until pH 7 was reached at 60-90 ° C. The process of saturation and gel appearance is 12 hours. The suspension was centrifuged, washed and filtered to remove soluble salts. The washing step was repeated two more times, after which the gel was dried in a spray dryer under vacuum and a temperature of 500 ° C.

The solutions after centrifugation and washing of the gel are mixed and separated as an alkali. The composition of the lye in wt. % e: Na ₂ O - 26.69; A1 ₂ O ₃ - 14.89; SiO ₂ - 7.2; Cl - 40.86; K ₂ O - 1.45; CaO - 4.52; FeO - 3.71.

Claims (4)

Patent claims A method of processing copper slag containing iron silicate - fayalite, comprising oxidizing fayalite in air, decomposing it into a mixture of iron oxides and silica and treating the resulting mixture with sodium hydroxide solution, characterized in that the felite from the slag is oxidized and decomposed to iron oxides and silica at a temperature of 800 to 850 ° C and a duration of 3 to 5 hours, the oxidized slag is mixed with a solution of sodium hydroxide in water with a concentration of 30-90 g / Ι and subjected to extraction in an autoclave at a temperature of 160 to 250 ° C, autogenous water vapor pressure of 0.6 to 4 MPa, with continuous stirring and a process duration of 3-9 h, during which the silica is dissolved in sodium hydroxide to obtain a reaction liquid phase containing sodium silicate, after which the liquid phase is separated and the solid phase of iron oxides is subjected to re-extraction in an autoclave by washing with water at a temperature of 150 to 250 ° C, auto water vapor gene pressure from 0.6 to 4 MPa and with continuous stirring, the resulting suspension is subjected to vacuum filtration, the solid phase of iron oxides is separated for pelleting, and the liquid phase, consisting of sodium silicate solution, is mixed with the reaction liquid phase from the first extraction and subjected to treatment by acidification with hydrochloric acid to release colloidal silicon hydroxide, which polymerizes and condenses to a gel, after which the resulting colloidal system is centrifuged, washed to remove soluble salts and filtered to separate the gel, which is subjected to drying to obtain fine, powdered amorphous silica (silica gel). Process according to Claim 1, characterized in that the acidification is carried out with hydrochloric acid at room temperature until pH 2 is reached, wherein the process of saturating and separating the gel is 12-24 hours. Method according to claim 1, characterized in that the acidification is carried out with hydrochloric acid at a temperature in the range from 60 to 90 ° C until a pH of 6 is reached, wherein the process of saturation and separation of the gel is 6-12 hours . Method according to one of Claims 1 to 3, characterized in that the drying of the gel is carried out in an oven at 60-90 ° C for 24-48 hours or in a spray drying installation under vacuum and temperature 300-800 ° C.