Treatment method of sulphide concentrates containing precious metals

FIELD: metallurgy.

SUBSTANCE: method involves leaching with further separation of non-soluble residue from the solution, its drying and further melting when it is mixed with sodium carbonate, silicon-containing flux, borax so that alloy of precious metals and slag is obtained. At that, original concentrate is subject to leaching by means of nitric acid solution. Melting is performed using the addition of sodium chloride to mixture. Concentrate is leached using nitric acid solution with mass concentration of 350-550 g/l. Sodium chloride is added to mixture for melting purpose in quantity which is more by 10-20% than stoichiometric quantity as per lead chloride obtaining reaction.

EFFECT: improving the extraction of precious metals; obtaining purer alloy and reducing the sulphide concentrate treatment costs.

3 cl, 4 tbl, 1 ex

The invention relates to the field of metallurgy of noble metals (BM), in particular to the processing of gravitational sulfide concentrates containing precious metals.

In the process of concentrating ores and Sands containing BM, get rich gravitational concentrates, the so-called "Golden head", which is a mixture of minerals and fragments of rocks, represented by sulphides (pyrite, arsenopyrite, Galena, chalcopyrite, sphalerite, and the like), oxides and hydroxides of iron (magnetite, hematite, limonite, goethite), metal scrap (RUB in the process of grinding ore) and the group of oxides of silicon, aluminum, calcium, magnesium. Noble metals (gold, silver and platinum group metals) relatively large size are present, usually in native form. Mass fraction of BM in the gravitational concentrates depending on the degree of finishing an average of 5.0 to 20.0% in total.

The method for extracting noble metals from gravity concentrates (SU # 1649815, MCP SW 11/02, published 09.01.1995), including oxidative roasting of the concentrate at a temperature of 500-700°C, the resulting calcine is mixed with sodium carbonate, silica flux quartz sand and carbonaceous reducing agent and melted at a temperature of 1200°C To produce alloy BM and slag.

Common signs of this Declaration, the by the way are similar use in the smelting of the charge, containing sodium carbonate and silica flux.

The disadvantages of this method are the high costs associated with carbon capture and disposal of sulfur dioxide (SO₂) kiln gases, increased loss of BM with dust operation firing and receiving contaminated alloys and refractory slag from smelting slag, a waste concentrate.

As the prototype accepted method for processing concentrates containing BM and sulfides (RU # 2395598, IPC SW 11/02, published 27.07.2010).

According to the method concentrate containing BM and sulfides, subjected to heat treatment in a mixture with nitrate and sodium carbonate in the ratio 1:(0,5-1,6):(0,1-0,4) at a temperature of 400-600°C with getting SPECA, which is leached in water and subsequent separation from the solution of the insoluble precipitate and drying, then the residue is melted at a temperature of 1200°C with sodium carbonate, silica flux and carbonaceous reducing agent with the addition of borax and calcium oxide with obtaining alloy BM and slag.

The General features of the proposed method with the prototype components are included in the composition of the mixture used for smelting with an insoluble precipitate, namely, sodium carbonate, silica flux, borax.

The disadvantages of this method are the high costs associated with the use of high temperatures, a considerable mass produced and voltage is supplied to the melting insoluble solid residues, as well as getting enough clean alloy BM.

The task, which is aimed by the invention is the reduction of costs for the processing of sulfide concentrates containing BM, increasing extraction BM in the alloy and the more pure noble metal alloy.

The technical result of the claimed invention lies in the exclusion of the operation of thermal decomposition, reduction poplavskii burden and to improve the content of the BM in the alloy during the melting of the mixture to obtain alloy BM.

The technical result is achieved in that in the method of processing sulphide concentrates containing BM, including leaching and subsequent separation from the solution of the insoluble precipitate, drying and subsequent fusion with sodium carbonate, silica flux, brown with obtaining noble metal alloy and slag according to the invention subjected to leaching of the original concentrate and lead his solution of nitric acid, and the melting is performed with the addition of the mixture of sodium chloride.

The difference of the proposed technical solutions from the prototype is the exception to the operation of the heat treatment, the introduction of a new operation leaching source of the concentrate solution of nitric acid and introducing the mixture to the melting of sodium chloride to obtain the CPF is VA precious metals and slag.

Physico-chemical essence of the proposed method is based on the fact that nitric acid is an effective oxidizer and the interaction with sulfides forms a water-soluble non-ferrous metals. The exception is lead sulphide (Galena), which decomposes with the formation of insoluble lead sulfate (PbSO₄). After nitrate leaching sulfide concentrate ("Golden head"), get the solution, which passes most of the metal impurities (including components and man-made scrap - iron and copper), and a solid residue (cake), which are concentrated BM, insoluble oxides (silicon, iron, aluminum and the like) and sulphate of lead. During the subsequent melting of the dried insoluble sludge (cake) in the alloy together with the BM goes, and part of the lead, as in the widely used chamotte or silicon carbide crucible during the melting process creates a restorative environment. To reduce the transition of lead in the alloy to be melted in the mixture add the sodium chloride, the melting process is formed volatile chloride of lead by the reaction:

PbSO₄+2NaCl→Na₂SO₄+bl₂↑

The effect of reducing the losses of precious metals and reduce processing costs is:

- due to the exclusion of high-temperature heat treatment operations and, as a consequence, the claim is Uchenie dust;

- due to the weight reduction poplavskogo of sediment and, therefore, reduce the mass of the produced slag;

- due to the low extraction BM in a solution of nitrate leaching (mass concentration of gold in solution does not exceed 0.01 mg/l and silver 1-2 mg/l).

To reduce the lead content of the alloy to well-known low-melting a mixture consisting of sodium carbonate, borax and silica flux, add necessary and sufficient sodium chloride 10-20% more than the stoichiometric amount on presents reactions obtain the chloride of lead.

Conditions nitrate leaching original concentrate selected according to the results of experimental data and depend on the particle size and mineral composition of the original concentrate. Relatively low values of the mass fraction of sulphides (10-40%) and grain size less than 0.3 mm (0.3 mm) allows nitrate leaching when the mass concentration of nitric acid 350-400 g/l, with a ratio of W:T=5 or 6:1 and a temperature of 60-70°C. With a relatively high fraction of total mass of sulphides (60-90%) and grain size less than 0.5 mm-0.5 mm) of the original concentrate, it is necessary and sufficient to carry out nitrate leaching when the mass concentration of nitric acid 500-550 g/l, with a ratio of W:T=7-8:1 and a temperature of 60-80°C.

Comparative analysis of the proposed method by prototipo shows that the claimed method differs from the known exception of the operation of the heat treatment, the introduction of a new operation leaching solution of nitric acid and the mixture to be melted to obtain a noble metal alloy and slag.

To prove compliance of the claimed invention, the criterion of "inventive step", a comparison was made with other technical solutions known from the sources included in the prior art.

The inventive method of processing sulphide concentrates containing precious metals, meets the requirement of "inventive step", as it provides lower costs for processing of concentrates and improving the content of precious metals in the resulting alloy, which is not obvious from the prior art.

Examples of using the proposed method.

For experimental verification of the proposed method used the gravitational sulfide concentrates - "Golden head", obtained during the concentration of gold-bearing ores. The compositions of the concentrates are shown in table 1.

Source concentrates were videlacele solution of nitric acid (350-550 g/l) in a glass flask with a stirrer at a temperature of 60-80°C, duration of leaching was 6-8 hours the Slurry was filtered, the insoluble sludge (cake) was washed with water, dried and weighed.

The dried cake was mixed with flux, then the mixture was placed in a fireclay crucible and melted in a shaft furnace of the resistance with micro-grain tungsten is kremnievye heaters for 45-60 min at a temperature of 1200-1250°C.

At the end of the melting crucible was removed from the furnace and cooled. The products of melting - furnace slag and alloy BM knocked out of the crucible and weighed. Intermediate and final products of the experiments were analyzed for content items assay, chemical and atomic-absorption methods of analysis.

The results of the experiments processing gravitational concentrates by the claimed method are shown in tables 2 and 3.

The results of examples on nitrate leaching (table 2) show the full decomposition of sulphides and industrial scrap (grated during grinding of metallic iron from the balls) and obtaining the precipitation of insoluble mass smaller than the original concentrate in 2 and 5 times. Moreover, for smaller gravity concentrate And enough lead nitrate leaching with a mass concentration of acid 350-400 g/l, and to concentrate larger and containing more sulfides, respectively, 500-550 g/l

Melting the dried cake of the proposed method: heat 2 and heat No. 4 (table 3) provides an opportunity to obtain an alloy with a mass fraction of noble metals 96,6 of 97.8%. When this mass fraction in the alloy of lead does not exceed 3.0 per cent (according THE 117-2-7-75 of lead in the alloy should be not more than 5.0%).

In the case of melting cake on the well-known charge (i.e. without the addition of sodium chloride), heat No. 1 (table 3), and adding to the mixture an insufficient amount of sodium chloride (80% of the stoichiometric amount) heat No. 3 (table 3), results in alloys with high mass fraction of lead, respectively, to 21.7% and 8.1%, therefore these alloys require additional purification in the process of refining.

The mapping process parameters declared and known methods of processing carried out for concentrates groups B, due to the similar content of Galena (PbS).

By the present method of processing total costs will be less than:

- by reducing (more than 4 times) mass poplavskii charge;

- due to the exclusion of the heat treatment operation, the original concentrate at a temperature of 400-600°C.

In that the face 4 shows comparative data processing gravitational concentrates by the claimed method and method adopted for the prototype.

The use of the invention improves the extraction of noble metals, to obtain Itok with a high content of noble metals, as well as to reduce costs for the processing of sulfide concentrates.

1. Method for processing sulfide concentrates containing precious metals, including leaching and subsequent separation from the solution of the insoluble precipitate, drying and subsequent melting in a mixture with sodium carbonate, silica flux, brown with obtaining noble metal alloy and slag, wherein the leaching is subjected to initial concentrate and lead his solution of nitric acid, and the melting is performed with the addition of the mixture of sodium chloride.

2. The method according to claim 1, characterized in that the leaching of lead concentrate the nitric acid solution with a mass concentration of 350-550 g/l

3. The method according to claim 1, characterized in that the charge for melting insoluble precipitate add sodium chloride in the amount of 10-20% more than the stoichiometric amount for reaction obtain the chloride of lead.