RU2539813C1 - Method of manganese ore processing - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves charge obtainment by mixing ore with sodium hydrosulphite in amount stoichiometrically necessary to bind manganese and impurities to sulphates. Then cinder is annealed and leached by water at 60-90°C for 0.5-1.0 hour at cinder to water weight ratio of 1:(3-4) and manganese and impurity transfer to solution. After bleaching, the solution is filtered, the filtrate is processed with sodium carbonate solution and flushed, the sediment is dried to obtain concentrated manganese. Filtrate comprised by sodium sulphate is fed to sulphur anhydride removal from flue gas and further to sodium hydrosulphite recuperation and to charge production. As a source ore, manganese oxide-carbonate ore is used, after mixing with hydrosulphate the charge is ground to 0.0-0.5 mcm grain size and agglomerated. Agglomerated charge is annealed at 500°C for 3 hours. Filtrate obtained after water bleaching is treated with 20% sodium bicarbonate solution in order to bind and deposit manganese, magnesium and aluminium salts. Remainder after water bleaching is flushed with water, dried and forwarded to coloured concrete production.

EFFECT: cost-efficient drainless technology of manganese oxide-carbonate ore processing.

2 cl, 1 dwg, 12 tbl, 1 ex

Description

The invention relates to a method for hydrometallurgical processing of poor carbonate-oxide manganese ores.

A known method of processing manganese raw materials (AS No. 1518400, class C22B 47/00, published in Bul. No. 40, 1989), including leaching of raw materials containing MnO _{2 with a} circulating solution of sulfuric acid or ammonium sulfate in the presence of ferromanganese as a reducing agent until pH = 1.8-2.0; separation of the insoluble residue from the solution by filtration, purification of the filtrate from impurities of iron and phosphorus by precipitation with ammonia at pH = 4.5-5.0. The separation of manganese from the purified filtrate is carried out by electrolysis; circulating sulfuric acid is returned to the leaching stage.

The disadvantage of this method is the high corrosivity of the reaction mass due to the use of a solution of sulfuric acid and the need for ferromanganese, and a significant amount of wastewater.

A known method of processing Mn-containing raw materials, including leaching it with 70-98% sulfuric acid in the presence of 20-40% potassium bisulfate solution used as a reducing agent. The resulting suspension is filtered. Manganese carbonate is precipitated from a filtrate containing manganese sulfate with a solution of potassium carbonate. The suspension is filtered, the precipitate is washed, dried and calcined at 650 ° C to obtain a manganese concentrate. The use of a solution of potassium bisulfate can reduce the consumption of sulfuric acid and improve the quality of the finished product (Patent RU No. 2223340, class C22B 47/00, C22B 3/08, publ. 02/10/2004). The disadvantage of this method is the use of expensive potassium bisulfate as a reducing agent, a large amount of effluent sent for disposal.

The closest to the achieved result is a method of processing manganese ore, including grinding the ore - mixing the crushed ore with sodium hydrogen sulfate, taken in the amount stoichiometrically necessary for the binding of manganese and impurities to sulfates. The resulting mixture is fired in three stages:

Stage 1 - at 200-300 ° C for 1-2 hours;

Stage 2 - at 400-500 ° C for 0.5-1.5 hours;

Stage 3 - at 600-700 ° C for 2-4 hours.

The pitch is leached with water at 40-80 ° C for 0.5-1.0 hours and the ratio of pitch: water = 1: (3-4). The pulp is filtered. Sludge containing aluminum hydroxide and silicon dioxide is washed, dried and sent for processing to obtain building material.

The filtrate, after separation from the precipitate, is treated with a solution of sodium carbonate to bind and precipitate the compounds of manganese (II) and iron (II).

After filtering the resulting suspension, the precipitate is washed, dried and, as a finished product, manganese concentrate (containing MnCO ₃ to 80.0%, FeCO ₃ to 23.0%, Na ₂ SO ₄ to 1.0% and H ₂ O - up to 1.0%) stock.

[RF patent No. 2441086, publ. 01/27/2012]

The disadvantage of this method of processing manganese ores are:

- processing only oxide ores;

- long-term, three-stage processing of the crushed mixture at high temperatures for 3.5-7.5 hours, which leads to a decrease in the productivity of the process and an increase in the cost of electricity and heat;

- the sulfatization process proceeds in an acidic environment, which in turn increases the corrosivity of the main processing equipment;

- in the process of firing the mixture at a temperature of 700 ° C for 7.5 hours, part of the sodium hydrosulfate may decompose due to a local temperature increase in the reaction mass above a predetermined temperature of 700 ° C. The decomposition will obviously proceed according to the scheme:

2NaHSO ₄ → Na ₂ S ₂ O ₇ → Na ₂ SO ₄ + SO ₃

260 ° <T <760 °

This circumstance will be especially important in large-tonnage production.

The technical task of the claimed invention is the development of a cost-effective and drainless technological scheme for processing manganese ores.

The technical result is achieved in the proposed method for processing oxide-carbonate manganese ore, including: obtaining a mixture by mixing the original ore with sodium hydrogen sulfate, grinding the mixture to particle sizes of 0.0-0.5 mm, calcining the mixture at 500 ° for 3 hours, water leaching caking and transferring a solution of manganese salts and its accompanying impurities, separating sludge by filtration, precipitating manganese compounds with an aqueous solution of sodium carbonate, isolating manganese concentrate, washing, drying and packaging the finished product and - manganese concentrate.

The method is as follows: (see. The basic technological scheme of the processing of oxide-carbonate manganese ore of the Ulu-Telyak deposit).

Natural manganese ore (mineralogical and chemical compositions, see table 1 and table 2) is ground together with sodium hydrosulfate NaHSO ₄ to a particle size of 0.0-0.5 mm. The necessary ratio of ore and sodium hydrogen sulfate for the binding of manganese oxides and impurities was adopted after stoichiometric calculations.

The mixture is agglomerated to avoid dusting, calcined at 300-500 ° C for 3 hours and leached for 0.5-1.0 hours with water (or a weak solution of sodium sulfate) at a ratio of T: W = 1: (3-4) . The resulting suspension is filtered, the filtrate is an aqueous solution of manganese, magnesium, aluminum, sodium sulfates, treated with a 20.0% aqueous solution of sodium carbonate at 30-45 ° C, and a solid residue consisting of calcium sulfate, silicon dioxide, iron oxides and other salts are washed, dried at 110 ° C and packaged (as a product for the production of colored concrete).

After processing the solution with sodium carbonate, the resulting suspension is filtered, the precipitate of manganese, magnesium carbonates and aluminum hydroxide is washed, dried and (as a finished product, manganese concentrate) is packed.

The filtrate is sent to the purification of exhaust gases from SO ₃ , and then to the regeneration of sodium hydrosulfate. Regeneration is carried out by adding spent sulfuric acid to the solution (5.0% excess according to the scheme).

Equimolecular Amounts

Na ₂ SO ₄ + H ₂ SO _{4 decom} → 2NaHSO ₄ .

The solution is evaporated or sent to leach the calcined charge, crystallize and centrifuged. Part of the NaHSO ₄ crystals is sent for mixing with the initial ore, and the excess is agglomerated and, as a finished product, is used in non-ferrous metallurgy (as a flux), or in the petrochemical industry (for whitening petroleum oils).

The essence of the invention is as follows: in the process of firing the mixture at a temperature of 300-500 ° C for 3 hours in the reaction mass, the following solid-phase reactions take place, in which sodium hydrosulfate acts as a flux, since it converts sparingly soluble oxides of manganese, magnesium and aluminum into readily soluble salts of sulfates .

Process chemistry

2NaHSO ₄ → 2NaHSO ₄ (melt) Na ₂ S ₂ O ₇ (pyrosulphate) + H ₂ O Na ₂ S ₂ O ₇ (melt pyrosulphate)

The molten sodium pyrosulfate reacts with oxides of manganese, magnesium, aluminum and calcium carbonate according to the scheme:

1. MnO ₂ + 4NaHSO ₄ → MnO ₂ + 2Na ₂ S ₂ O ₇ + 2H ₂ O → MnSO ₄ + 2Na ₂ SO ₄ + SO ₃ ↑ + 0,5О ₂ ↑ + 2H ₂ O ↑

2. Mn ₂ O ₃ + 4NaHSO ₄ → MnSO ₄ + 2Na ₂ SO ₄ + 2H ₂ O + 0,5O ₂

3. CaCO ₃ + 2NaHSO ₄ → Na ₂ SO ₄ + CaSO ₄ + CO ₂ + H ₂ O

4. Al ₂ O ₃ + 6NaHSO ₄ → Al ₂ (SO ₄ ) ₃ + 3Na ₂ SO ₄ + 3H ₂ O

When leaching, aluminum sulfate Al ₂ (SO ₄ ) ₃ undergoes hydrolysis and precipitates in the form of aluminum hydroxide:

Al ₂ (SO ₄ ) ₃ + 6H ₂ O → 2Al (OH) ₃ + 3H ₂ SO ₄

5. MgCO ₃ + 2NaHSO ₄ → MgSO ₄ + Na ₂ SO ₄ + H ₂ O + CO ₂ .

Silicon dioxide and iron oxides do not interact under these conditions and precipitate, and the salts of manganese and magnesium (sulfates) dissolve well in water (leach out).

The processing of manganese ore according to the proposed method ensures the simplicity of the process by combining the stages of calcining the mixture and obtaining water-soluble salts of manganese, removing iron oxides from the reaction mass, a drainless processing scheme by trapping sulfur oxides from the exhaust gases, recycling sodium hydrosulfate and returning it to the process process.

Using the claimed invention will allow to obtain a technical result, which consists in the possibility of obtaining high-quality target product - manganese concentrate and related products - sodium hydrosulfate and raw materials for the production of colored concrete.

The effectiveness of the developed technology and the selected process parameters: the fineness of the grinding of the mixture, the duration and temperature of its calcination, the duration and temperature of water leaching, the ratio T: W and the content of sodium hydrogen sulfate in the mixture were evaluated by the concentration of manganese oxides in the mixture, manganese sulfate in an aqueous solution and the concentration of carbonate Manganese in the finished product.

Tables 3 and 4 show the results of tests to determine the effect of the fineness of the grinding of the charge and the temperature and time of its calcination on the concentration of manganese oxides and manganese sulfate in solution in it.

The mineralogical and chemical compositions of the test ore are given in Tables 1 and 2. Previously, before grinding, the ore was mixed with sodium hydrogen sulfate in the ratio of ore: sodium hydrogen sulfate = 1: 2.6 and crushed to particle sizes of 0.0-1.0 mm. The crushed mixture was calcined at a temperature of 500 ° C for 3 hours and leached at a ratio of T: W = 1: 4.

The concentration of manganese oxide in the ore before testing was 10.73%.

Table 3 shows that when grinding the mixture to a particle size of less than 0.5 mm, almost all manganese oxide passes into water-soluble manganese sulfate, and with a particle size of up to 1.0 mm, the residual MnO ₂ content in the mixture was 3.1%, and only 83.7% switched to MnSO ₄ .

The effect of temperature and duration of calcination of the charge on the concentration of manganese oxide in it is shown in Table 4.

For example, the process of calcining the mixture at a temperature of 500 ° C for 3 hours ensures the completeness of solid-phase chemical reactions and the transition of manganese oxides to a water-soluble form — to manganese sulfate (see Table 4, which shows the almost complete absence of MnO ₂ in an aqueous solution after calcining the mixture at 500 ° C and for 3 hours).

The decrease in temperature and the duration of calcination of the charge does not ensure the complete transition of manganese oxides to a water-soluble form and, therefore, leads to a decrease in the yield of the target product — manganese concentrate.

An increase in temperature and duration of the calcination process above 500 ° C and more than three hours leads to an excessive consumption of heat and an increase in the cost of the entire technological process.

The consumption of sodium hydrosulfate below stoichiometrically necessary leads to a decrease in the conversion of oxides to a water-soluble form, and, consequently, to a decrease in the yield of the finished product.

The leaching process at a mass ratio of T: L = 1: (3-4) at 60-90 ° C for 0.5-1.0 hours ensures almost complete dissolution of manganese, magnesium, aluminum sulfates and a high yield of product.

Example 1. 1000 g of oxide-carbonate manganese ore is mixed with 2600 g of sodium hydrogen sulfate, crushed to a particle size of 0.0-0.5 mm and calcined at 500 ° C for 3 hours. The mineralogical and chemical composition of the ore, as well as the chemical composition of the mixture before and after calcination, see Tables 1, 2, 5. The amount of sodium hydrosulfate 2600 g was taken in the stoichiometric amount required for the binding of Mn, Mg, Al, and Ca to sulfates.

In the process of calcination in the gas phase are released, g: SO ₃ - 99,0; water vapor - 208.0; 0.5 O ₂ - 20.0 and CO ₂ - 350.0 (see table 5). The calcined charge, weighing 2934 g, is leached with water at a ratio of T: W = 1: 4 for 3 hours. The flow rate of water or a weak aqueous solution of sulfates amounted to 11738 g, part of the water evaporated at contact with the hot mixture - 2936 g (see material leaching balance, Table 6), and the temperature of the calcined charge was 60-80 ° C. The suspension is filtered. The precipitate, weighing 1136.2 g (composition, g: Fe ₂ O ₃ - 37.3; CaSO ₄ - 1048.0; MgSO ₄ - 3.4; SiO ₂ - 47.45), washed, dried at 110 ° and pack (as raw materials for the preparation of colored concrete). The filtrate, weighing 10601 g (composition, g: MnSO ₄ - 194.2; Al ₂ (SO ₄ ) ₃ - 40.0; MgSO ₄ - 27.1; Na ₂ SO ₄ - 1537.0 and water - 8803.0 ) The filtrate is treated with a 20.0% sodium carbonate solution at 30-40 °. The suspension is filtered. The precipitate, weighing 170 g (composition,%: MnCO ₃ - 87.2; Al (OH) ₃ - 1.8; MgCO ₃ - 11.0), washed, dried at 110 ° C, and, as a finished product, manganese concentrate, pack. Manganese concentrate complies with TU U 13.2-00190911-002: 2009 (see Volume 7). Manganese-ore oxide-carbonate concentrate: grade 1, contains,%: Mn - 41.6; Al ₂ O ₃ - 1.3; MgO - 5.3. This product can be widely used in the production of blast furnace ferromanganese, metallic manganese, electric furnace, etc. (see table 12).

After separation of the commercial product, the filtrate, weighing 11243 g (composition, g: Na ₂ SO ₄ - 1752; H ₂ SO ₄ - 32.0 and H ₂ O - 9461), is sent to purify the exhaust gases from 99 g SO ₃ (see table 8) and further - on the regeneration of sodium hydrosulfate (see table 9). The regeneration of sodium hydrogen sulfate is carried out by mixing 11342 g of an aqueous solution of sulfates with 3025 g of a 40.0% solution of spent sulfuric acid (with a 5.0% excess of H ₂ SO ₄ ). An aqueous solution of NaHSO ₄ - 14367 g, composition,%: NaHSO ₄ - 20.6 and H ₂ O - 79.4, evaporated, crystallized and the crystals were separated by centrifuges (see tables 10 and 11).

Crystals of NaHSO ₄ , weighing 2600 g, are sent to the preparation of the mixture, and an excess of 360 g is dried, agglomerated and, as a finished product, used in non-ferrous metallurgy (as a flux) or in the oil industry (for whitening petroleum oils).

Thus, in the processing of 1000 g of the Ulu-Telyak oxide-carbonate manganese ore according to the claimed technology, the following was consumed:

1. Sodium bisulfate - 2600

2. Sodium carbonate - 160

3. 40.0% sulfuric acid - 1209

4. Water - 12378, including:

- for leaching the mixture - 11738 g

- for the deposition of sulfates of manganese, magnesium and aluminum hydroxide - 640.0.

In this case, a marketable product was obtained, g:

- manganese concentrate - 170.0

- raw materials for non-ferrous concrete - 1136,0

- sodium bisulfate - 2960.0

(see diagram)

Table 1 Mineralogical composition of oxide-carbonate ore deposits Ulu-Telyak The name of the mineral Chemical formula Mineral content, mass fraction,% 1. Quartz SiO ₂ 8.0 2. Psilomelan nMnO * MnO ₂ * nH ₂ O 10.0 3. Ransjeit (CaMn) Mn ₄ O ₉ * 3H ₂ O 7.0 4. Vernadite MnO ₂ * H ₂ O 11.0 5. X-ray amorphous phase - 54.0 6. Clay component 10.0 100.0

table 2 The chemical composition of the feedstock Name of components Content, mass fraction,% MnO ₂ 10.73 Mn ₂ O ₃ 0.42 CaCO ₃ 77.05 Fe ₂ O ₃ 3.73 Al ₂ O ₃ 1.19 SiO ₂ 4.745 MgCO ₃ 2.135 100.0

Table 3 The effect of fineness grinding mixture on the content of MnO ₂ and manganese sulfate in solution The residual content of MnO ₂ in the mixture,% The amount of manganese oxide transferred to the solution in the form of MnSO ₄ ,% Fraction <0.3 mm 0,0 100.0 Fraction <0.5 mm 0,0 100.0 Fraction <1.0 mm 3,1 83.7

Table 4 The effect of temperature and duration of calcination of the mixture on the concentration of MnO ₂ in solution The content of MnO ₂ in aqueous solution,% The duration of the calcination of the charge, hour Calcination Temperature, ° C twenty 300 400 450 475 500 600 700 one 10.73 6.2 5.3 4.1 2,3 0.26 0 0 2 - 6.3 5.2 4.2 2,3 0.22 0 0 3 - 6.3 5.2 4.2 2,3 0.01 0 0

Table 5 The material balance of the process of calcining the mixture at 500 ° C for 3.0 hours The composition of the mixture before calcination
%
g The composition of the mixture after calcination
%
g 1. Manganese ore 1000,0 1. The charge 2934 27.8 100.0 Composition: 107.3 3.0 Composition: MnO ₂ 4.2 0.12 MnSO ₄ 194.2 6.62 Mn ₂ O ₃ 770.5 21,4 Fe ₂ O ₃ 37.3 1.27 CaCO ₃ 37.3 1,04 Al ₂ (SO ₄ ) ₃ 40,0 1.36 Fe ₂ O ₃ 11.9 0.33 SiO ₂ 47.45 1,62 Al ₂ O ₃ 47.45 1.31 CaSO ₄ 1,048.0 35.7 SiO ₂ 21.35 0.60 MgSO ₄ 30.5 1,04 MgCO ₃ Na ₂ SO ₄ 1537 52,4 2. NaHSO ₄ 2600.0 72,2 2. flue gases 665.5 composition: SO ₃ 99.0 Water vapor 208.0 0.5 O ₂ 20,0 CO ₂ 338.5 Total: 3600 100.0 Total: 3600 100.0

Table 6 The material balance of the leaching process of the mixture Coming g % Consumption g % 1. The charge after 2934.5 20,0 Suspension after 14673 100.0 calcination leaching including MnSO ₄ 194.2 6.62 1. Sediment 1136.2 Fe ₂ O ₃ 37.3 1.27 composition: Al ₂ (SO ₄ ) ₃ 40,0 1.36 Fe ₂ O ₃ 37.3 3.3 SiO ₂ 47.45 1,62 CaSO ₄ 1,048.0 92.2 CaSO ₄ 1,048.0 35.7 MgSO ₄ 3.4 0.3 MgSO ₄ 30.5 1,04 SiO ₂ 47.45 4.2 Na ₂ SO ₄ 1537.0 52,114 Total 2934.5 100.0 Total 1136.2 2. Water for 11738 2. The filtrate, including 10601 leaching salt composition: 1798 MnSO ₄ 194.2 1.43 Al ₂ (SO ₄ ) ₃ 40,0 0.3 MgSO ₄ 27.1 0.2 Na ₂ SO ₄ 1537.0 11.35 Water 8803 86.7 3. The water evaporated 2935 Total: 14673 Total: 14673

Table 7 Precipitation of carbonates of manganese and magnesium and aluminum hydroxide Coming g % Consumption g % 1. Aqueous solution 10601.0 93.0 1. Sediment 169.7 1.39 salts (filtrate) Including: Including: MnCO ₃ 148.0 87.2 MnSO ₄ 194.2 1.83 Al (OH) ₃ 3.0 1.8 Al ₂ (SO ₄ ) ₃ 40,0 0.38 MgCO ₃ 18.7 11.0 MgSO ₄ 27.1 0.26 Na ₂ SO ₄ 1537.0 14.5 2. The filtrate 11243 98.61 H ₂ O 8803 83.0 including: 2. 20% solution Na ₂ SO ₄ 1752 15.6 sodium bicarbonate 800,0 7.0 H ₂ O 9461 84.1

including: H ₂ SO ₄ 32 0.3 Na ₂ CO ₃ 160,0 20,0 H ₂ O 640,0 80.0 Total: 11415 100.0 Total: 11415 100.0

Table 8 Material balance of exhaust gas purification from SO ₃ Coming    g    % Consumption    g    % 1. SO ₃ 99 0.9 Water solution 11344 100.0 2. The filtrate after 11245 99.1 sulfates cooling Including: carbonates including: 1752 H ₂ SO ₄ 153 1.35 Na ₂ SO ₄ 9461 Na ₂ SO ₄ 1752 15,5 H ₂ O 32 H ₂ O 9437 83.15 H ₂ SO ₄ 11344 100.0 11344 100.0 Total: Total:

Table 9 Material balance of the hydrosulfate regeneration process Regeneration proceeds according to the scheme: Na ₂ SO ₄ + H ₂ SO ₄ (5.0% excess) → 2NaHSO ₄ Coming g % Consumption g % 1. Aqueous solution 11342 78.9 1. NaHSO ₄ 2961.0 20.6 after purification of gases from SO ₃ composition: 153.0 1.35 H ₂ SO ₄ 1752.0 13.5 Na ₂ SO ₄ 9437 83,2 H ₂ O 1. Sulfuric acid 3025,0 21.1 2. H ₂ O 11406 79,4 spent, 40% (5.0% excess) including: H ₂ SO ₄ 1209,0 40,0

H ₂ O 1816.0 60.0 Total: 14367 100.0 Total: 14367 100.0

Table 10 The material balance of the evaporation of the solution after regeneration of hydrosulfate Coming   g   %     Consumption   g   % Aqueous solution including: 14367 100.0 1. Juice Steam 10666 74,2 Na ₂ HSO ₄ 2961 20.6 2. Suspension composition: 3701 25.8 H ₂ O 11406 79,4 2961 80.0 NaHSO ₄ 740 20,0 H ₂ O Total: 14367 100.0 Total: 14307 100.0

Table 11 Material balance of crystallization and centrifugation of a suspension of sodium hydrogen sulfate and drying of crystals Coming g % Consumption g % Suspension after 3701 100.0 1. Uterine 648 17.5 parks solution structure: 2961 80.0 2. Crystals 3053 82.5 NaHSO ₄ 740 20,0 NaHSO ₄ H ₂ O including: 2961 95.0 NaHSO ₄ - 2961 92.0 5,0 H ₂ O - 92.0 Total: 3701 100.0 Total: 3701 100.0

Table 12 Properties of the finished product Finished product Content,%: MnCO ₃ - 87.2 Al (OH) ₃ - 1.8 MgCO ₃ - 11.0 The composition of the manganese concentrate,%: Mn - 41.6 Al ₂ O ₃ - 1.3 MgO - 5.3

The finished product according to TU U 13.2-00190911-002: 2009 manganese ore oxide-carbonate concentrate grade the content of Mn,% for production one 40-41.6 Ferromanganese blast furnace, manganese metal, electric furnace

Claims (2)

1. A method of processing manganese ores, including the preparation of a mixture by mixing ore with sodium hydrogen sulfate, taken in an amount stoichiometrically necessary for binding manganese and impurities to sulfates, calcining, leaching of the cinder with water at a temperature of 60-90 ° C for 0.5-1, 0 hours and a mass ratio of cinder: water equal to 1: (3-4) with transfer to a solution of manganese and related impurities, separating the insoluble precipitate by filtration, treating the filtrate with a solution of sodium carbonate, washing the resulting carbonate precipitate with water and drying with irradiation of the finished product in the form of manganese concentrate, the direction of the filtrate, which is sodium sulfate, to purify the exhaust gases from sulfuric anhydride, then to the regeneration of sodium hydrosulfate and its direction to prepare the charge, characterized in that as the initial manganese ore take oxide-carbonate manganese ore, after mixing with hydrosulfate, the mixture is crushed to a particle size of 0.0-0.5 mm and subjected to agglomeration, the agglomerated mixture is calcined and conducted at a temperature of 500 ° C in echenie 3 hours while processing the filtrate obtained after aqueous leaching solution of sodium carbonate are taken in an amount stoichiometrically required for binding and precipitation of salts of manganese, magnesium and aluminum. 2. The method according to claim 1, characterized in that the precipitate after water leaching, consisting of iron oxides, silicon dioxide, aluminum hydroxide and calcium sulfate, is washed with water, dried and sent to receive colored concrete.

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