Method for processing concentrates containing precious metals

 

The invention relates to the metallurgy of noble metals, in particular to the pyrometallurgical processing of concentrates containing gold and silver. Method for processing concentrates containing precious metals, is that the original concentrate mixed with brown, calcium oxide and silica flux, the mixture is melted and derived products - slag and gold-silver alloy is cooled and separated. What's new is that the composition of the mixture to be melted add the sodium sulfate, carbonaceous reducing agent, as silica flux use silica sand or silica glass in the melting process receive additional sulfide product - Stein. The method allows to increase the efficiency by increasing the content of gold and silver in the target grades. 3 table.

The invention relates to the field of metallurgy of noble metals (BM), in particular to the pyrometallurgical processing of concentrates containing gold and silver.

Target products gravity beneficiation process gold-bearing Sands and ores are placer gold and gold head. The composition of the obtained concentrates on a group of impurity comodi gold sand, containing pyrite (FeS2), arsenopyrite (FeAsS), chalcopyrite (CuFeS2), Galena (PbS), etc., sulfide components are primarily concentrated in the so-called industrial refining of concentrates, and placer gold. In the industrial refining of concentrates contain up to 8-10% of gold and silver, 5-15% sulphides, the rest of oxide minerals magnetite (Fe3About4), ilmenite (FiO3), quartz (SiO2), etc. In placer gold contains up to 1-4% sulphides, 3-8% oxide minerals, the rest of the gold and the silver.

When gravity processing of oxidized gold-bearing ores in the "Golden head" in the middle contains 10-25% of gold and silver, 50-60% of oxide minerals magnetite, limonite (Fe2About3H2O), quartz, and others, and up to 10-20% of metallic iron (scrap), native copper, oxide compounds of non-ferrous metals.

There is a method of processing of gold concentrates, including oxidative calcination of the material at 500-700oWith and subsequent melting of candle mixed with ash, silica sand and carbonaceous reducing agent with obtaining gold-silver alloy and slag [1]. The disadvantages of the method are significant losses of noble metals with pylegathon the manual processing of concentrates, containing precious metals, which is taken as a prototype, as the closest to the claimed technical solution [2].

According to the method of the initial concentrate is mixed with brown, calcium oxide and silica flux containing quartz sand, the mixture is melted at a temperature of 1200-1300oWith and obtained the condensed products - slag and metallic gold-silver alloy after deposition divided by the boundary.

The disadvantage of this method is the low degree of selection of precious metals from iron and non-ferrous metals, resulting in a higher content of non-ferrous metals and iron in the target gold-silver alloy.

The task, which is aimed by the invention, is to increase the efficiency of processing of concentrates containing precious metals, due to the increase in the content of gold and silver in the target alloys obtained in the process of melting of the source concentrates.

The problem is solved at the expense of achieving a technical result, which is to improve the selectivity of gold and silver from base metals and iron by concentrating the latest in the sulfide phase and the effective separation of Oh is carried out so that in a known method of processing concentrates containing precious metals, including original mix concentrate with brown, calcium oxide and silica flux, melting the mixture with obtaining gold-silver alloy and slag, and separating the condensed products of fusion, according to the invention, the mixture further comprises sodium sulphate and carbonaceous reducing agent, and as silica flux use silica sand or silica glass in the following ratio, wt.%: Borax - 15-30 calcium Oxide - 1,8-3,0 Silica flux - 3,2-33,2 Sulfate sodium - 2-10 Carbon reducing agent is 0.3 to 1.5 Concentrate containing precious metals - the Rest is in the process of melting receive additional condensed product is matte, which after cooling is easily separated from the slag and gold-silver alloy.

The difference of the proposed technical solutions from the prototype is the composition of the mixture to the melting of the original concentrate and getting a new condensed product melting - matte.

The purpose of the components of the mixture to the melting of the original concentrate the following. Borax (Na2B4O710H2O) is used as the Le is e on the boundary of the slag - Stein - metal, contributing to the coalescence of drops of gold-silver alloy and matte and release them from the slag phase. Quartz sand or silica glass is introduced to bind in a stable silicate complexes of the slag-forming components of the source and concentrates as a source of silica to the flow of the reaction sulfatirovnie. The sodium sulfate is used for the formation of sodium sulfide and sulfatirovnie non-ferrous metals and iron. Carbon is the reducing agent in the reaction sulfatirovnie.

The physico-chemical nature of the separation process of melting in the claimed method is based on the limited mutual solubility in the liquid and solid state of the metal gold and silver and polysulfide type Na2S-MenSmwhere Me is iron, copper, lead, zinc, and others.

The composition and formation of the matte phase at melting is the process adjustable and is determined by the composition of the original concentrate BM, the number of fluxes and additives in the charge. When heating and melting of the charge reactions proceed with selection as intermediate products of sodium sulfide and elemental sulfur by reactions 1-3:


When melted at a temperature of 1100-1200oWith primary sulfides contained in the original concentrates BM, and secondary sulfides, formed by reactions 1, 4, 5, form the matte phase melt. Slag-forming oxides are dissolved in an easily fusible slag on the basis of B2O3-Na2O-SiO2-CaO-CaF2-FenOm. Gold and silver form a metal gold-silver alloy, which stands out as the most difficult phase of the melt. After melting and cooling of the melt condensed products are easily separated by the boundary liquation phase separation. Gold-silver alloy is the target product, slag - conditionally otvajnym. Stein contains an average of about 1.0 to 1.5% of gold and up to 5-6% silver, is an intermediate product and is processed in known ways in order to extract BM.

The upper and lower limits of the content in a mixture of borax, calcium oxide and silica provide a flux in the smelting of concentrates, BM, respectively with high and low content of slag-forming componentone borax, of calcium oxide and silica flux in the mixture leads to an increase in residual BM in the slag at a flow rate below the proposed limit due to its refractoriness. The increase in the content of borax in a mixture of more than 30%, calcium oxide than 3% and silica flux above 33,2% impractical because not improve the performance of the heat.

The upper and lower limit of the content of sodium sulfate in the mixture provide smelting education necessary and sufficient sodium sulfide to its content in the matte at the level of 5-10% and a completeness of sulfatirovnie metallic iron and non-ferrous metals processing concentrates respectively with high and low contents of these components. When the content of sodium sulfate below 2% increases the content of impurities in the gold-silver alloy due to the incompleteness of their sulfatirovnie. The excess content of sodium sulfate for 10% leads to increased solifidian silver and increase its residual content in the matte.

The number added to the charge of carbonaceous reductant 0.3 to 1.5% by experimental data provides completeness for the processes of sulfatirovnie impurities and education necessary and sufficient Avraamova method with the prototype shows that the claimed method differs from the known to the introduction of new components in the mixture to the melting of sodium sulfate, carbonaceous reducing agent and of silicate glass and getting a new condensed product of a Stein.

To prove compliance of the claimed invention, the criterion of "inventive step" was compared with other technical solutions known from the sources included in the prior art. Using a carbon reductant in the mixture to be melted concentrate BM you know similar to [1], where the carbon is used to restore the Fe2About3FeO, which reduces the melting point of the slag and residual content of BM. In the inventive method, the carbonaceous reductant is spent on education matte, which gives way to new properties and new effects, such as enhancement of the selection of gold and silver from base metals and iron.

The inventive method of processing concentrates containing precious metals, meets the requirement of "inventive step", as it provides a high degree of selection of gold and silver from base metals and iron smelting concentrates BM. The result is higher efficiency equipment.

Examples of using the proposed method
For experimental verification of the proposed method used the fluxes and additives, crushed to a particle size less than 0.3 mm, and gold concentrates. Concentrate "And" middlings refining of concentrates obtained during the final cleaning of placer gold. Concentrate "B" placer gold obtained when the gravitational processing of gold-bearing Sands. Concentrate "In" - "the Golden head", obtained by gravitational enrichment of oxidized gold ore. The compositions of the concentrates are shown in table 1.

Prepared six charges, each a mass of 100.0 g, three of which corresponded to declare, and three incredible compositions. Each mixture was loaded into Szamotuly the crucible, melted and kept at a temperature of 1250oC for 60 min in furnaces with carbide heaters. After melting crucibles were removed from the furnace and cooled. Products smelting - slag, matte and gold-silver alloy was knocked out of the crucible. shared boundary liquation phases, weighed and analyzed for the constituents of the assay and chemical analysis methods.

Data on the composition of the charge, the outputs of smelting products, the content of gold is whether calcium fluoride (CaF2), the connection is similar to that of Cao properties, but allow a more fluid slag.

The obtained data show that the inventive method allows for the smelting of concentrates BM get targeted alloys with a high content of gold and silver due to the effective allocation of iron and non-ferrous metals in coexisting sulfide phase - Stein and the subsequent separation of these products. As follows from the obtained results, the inventive method provides for obtaining the target alloys with total content of gold and silver 92,94-99,42%. The transition from the claimed (op.1-3) to incredible mixes for smelting concentrates BM leads to the deterioration process or as a result of reducing the degree of selection of gold and silver from base elements, or because of irrational excess reagents.

An example of using the prototype method
To compare the performance of the proposed method and the method of the prototype spent experience processing concentrate "In" technology of the prototype method. The mixture to be melted contained (wt.%, grams): 36.0 concentrate "In"; 37,0 borax; 22,0 quartz sand; 5.0 calcium oxide. Smelting, separation and analysis of products was carried out by the above methods is 5 silver; 17,86 copper; 0.77 lead; to 9.57 iron. In the slag respectively contained, wt.%: 0,143 gold; 0,119 silver; 1,88 copper; 0.03 lead.

Comparison of indices from the use of declared and known methods are presented in table 3.

The data of table 3 show that using the proposed method allows to obtain the target alloys BM with higher content of gold and silver, which significantly reduced the costs of the subsequent processing of alloys otation.

For the proof of the criterion of "industrial application" should indicate that the proposed method is tested on a number of gold mining companies in Russia.

Sources of information
1. Patent USSR 1649815, CL 22 In 11/02, 1989.

2. RF patent 2086684, CL 22 In 11/02, 1997.


Claims

Method for processing concentrates containing precious metals, including original mix concentrate with brown, calcium oxide and silica flux, melting the mixture with obtaining gold-silver alloy and slag and separation of the products of melt, characterized in that the mixture further added sodium sulfate and carbonaceous reducing agent, and as kremnezemami the>Calcium oxide - 1,8-3,0
Silica flux - 3,2-33,2
The sodium sulfate - 2-10
The carbonaceous reducing agent is 0.3 to 1.5
The concentrate containing precious metals - Rest
the smelting of lead from obtaining as an additional product - matte.

 

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