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INVENTION
Russian Federation Patent RU2100458

METHOD FOR PROCESSING OF PRECIPITATION OF ZINC CONTAINING PRECIOUS METALS

METHOD FOR PROCESSING OF PRECIPITATION OF ZINC CONTAINING PRECIOUS METALS

Name of the inventor: Ermakov AV .; Sivkov MN .; Timofeev NI .; Kozhurki VN .; Nikitin VP .; Kuzmenko GF .; Zhizhin SM .; Dmitriev VA
The name of the patentee: Open Joint Stock Company "Ekaterinburg plant for processing non-ferrous metals"
Address for correspondence:
Starting date of the patent: 1996.05.13

Usage: As for the processing methods after precipitation carburizing cyanide solutions containing zinc and lead (the zinc precipitation). The inventive method comprises firing in an oxidizing atmosphere at a temperature of 750-850 o C for 30-75 minutes with mixing calcine the fluxing additives containing cryolite and / or borax in an amount providing a ratio of starting material to fluxing additive 1 :( 1,0-0,5) melting at a temperature of 1100-1250 o C it was held for at least 1 hour. This leads to the melting crucible with stirring with a stirrer, whose surface has a coating to provide improved wettability noble metal melt. The proposed method allows processing of zinc precipitation with high recovery of precious metals in a metal ingot, suitable for the manufacture of jewelry.

DESCRIPTION OF THE INVENTION

The invention relates to metallurgy of precious metals, in particular, to methods for processing precipitation after carburizing cyanide solutions containing lead and zinc.

Precipitation obtained after cementation noble metals from cyanide solutions, so-called zinc precipitation, is a complex heterogeneous mixture comprising noble metals, zinc, lead and their compounds and mineral impurities. Direct remelting zinc precipitation is possible only with small content of mineral impurities, since they increase the melting temperature increases and at temperatures above 135 o C is possible waste of precious metals, especially silver.

Public patent information from known processing methods similar materials containing precious metals. Known gold slimes treatment method [1], comprising mixing the sludge with fluxes and firing without stirring at a temperature of 350-450 o C to sinter the mass for subsequent melting of the particulate material. However, the known method can only be used effectively for gold sludge with a high content of gold or other metal-containing compounds.

The method for extracting noble metals [2] comprising calcining the starting material in the presence of sodium borohydride.

Known flux for melting and casting of alloys based on gold, silver and copper, containing up to 95% of boric anhydride and the balance silica (auth. St. USSR N 1528805, cl. The C 22 B 9/10, 17.01.88, publish. 15.12. 89. BI N 46).

Known methods provide for the extraction of the precious metals gold and silver, but the base is obtained ingot contaminated by impurities due to the fact that the flux used is not sufficiently accumulate impurities. The slag obtained by smelting, have high viscosity, resulting in losses with them significant amounts of precious metals.

A method of processing hard gold ores [3] The method relates to processing trudnopererabatyvaemyh materials containing precious metals and includes firing a starting material (calcine) and fluxes to melt the batch until complete melting. As the use of flux limestone and silicate materials at a ratio of CaO: SiO 2 in the starting material is greater than 1.

The disadvantage of this method is that lead to melting or vysokokremnezemistyh kaltsievosilikatnyh slags containing precious metals, which requires additional processing steps for processing slags. This leads to a reduction of the recovery of precious metals due to their dilution during further processing steps.

According to the technical essence and achieved result, the closest to the proposed object of the invention is a method for processing sediment obtained after the precipitation of gold from cyanide solutions [4] The method of precipitation includes firing in a muffle furnace and melting with fluxes in crucibles. The charge for melting up of soda, borax, silica sand and fluorspar. Melting was conducted for two hours.

The disadvantage of this method is receiving the ingot heavily contaminated by impurities, and low precious metal recovery into an ingot (86-90% gold and 83-85% silver), the slag contain a considerable amount of gold and require additional processing.

The task to be solved by the proposed technical solution is to allow processing of zinc deposits with a high degree of extraction in a metal ingot only of gold and silver.

The stated object is achieved in that a method for processing of zinc precipitation containing precious metals, comprising firing in an oxidizing atmosphere, melting sludge oxidized in the presence of fluxing additives to obtain molten metal according to the invention, calcination is carried out at 750-850 o C for 30 75 minutes, the oxidized product is mixed with the fluxing additives containing cryolite, or borax, or mixtures thereof in amounts to provide a ratio of the starting material 1 fluxing additive :( 1,0-0,5), melted at a temperature of 1100-1250 o C and kept under stirring for at least 1 hour, wherein a melting crucible furnace are coated with a stirrer, providing improved wettability noble metal melt. When used as a fluxing additive mixture of borax and cryolite they are taken in the ratio of 1 :( 0,7-0,3).

Precalcination provides initial precipitation of salts pyrolysis and oxidation of lead and zinc. These oxides improve slag formation and reduced melt viscosity. Without the operation of oxidizing roasting of the zinc and lead will move in precious metals bullion. The temperature of 750-850 o C is sufficient to transfer the impurities of lead and zinc in the oxide phase of the claimed exposure time. The optimal time of isothermal holding is determined by direct graviometricheskimi research: its increase more than 75 minutes is impractical since the end of the salt pyrolysis and oxidation of zinc and lead, and less than 30 minutes leads to incomplete transfer of the latter in the oxide phase and a partial shift in the bar during the subsequent smelting.

Melting calcine together with cryolite or brown, or mixtures thereof, having flyusoobrazuyuschimi properties, allows to process virtually any precipitation oscillation composition for zinc and lead, with the highest recovery of precious metals. These additives reduce the viscosity of the oxide melt (slag), thereby accelerating coagulation and precipitation of the melt droplets of precious metals. Cryolite lowers the viscosity and melting point of the resulting slag and prevents tangling therein noble metal particles, which due to the coagulation and coarsening freely settle on the bottom of the crucible, which ensures the purity of the metal phase. Introduction borax melt enhances adsorption processes in the melt, thus achieving the acceleration transition impurities into the slag. When used as an additive mixture of cryolite flyusoobrazuyuschey brown with additive effect most effectively by a combination of the above properties of a mixture of components in the claimed range.

Limiting the number of flyusoobrazuyuschih addition to the initial charge due to the optimization of the properties of the resultant oxide melt. Thus, when administered in a ratio of less than 1: 0.5 is obtained sufficiently viscous slag, which reduces the rate of precipitation and coagulation processes especially small metal droplets. by increasing the temperature, viscosity Reduced ineffective, as it leads to a frenzy of precious metals due to evaporation, or require additional technological methods to capture fumes containing precious metals and their subsequent extraction of fumes. Increasing the amount of flux in a ratio greater than 1: 1 leads to higher costs for processing received volume in more dump slag.

Embodiments of the melting process in the claimed temperature range for 1 hour to obtain the necessary melt (1100 o C) and allowing the binding of impurities and slag (1250 o C). At a temperature of more than 1250 o C the degree of separation of precious metals and impurities do not increase, but increases the loss of precious metals, particularly silver, by entrainment in the gas phase, which reduces the degree of its extraction into an ingot.

melt mixing and the use of stirrers with applied thereto and the inner surface of the refractory crucible coatings well wettable molten gold-silver, provides a greater increase in the area of ​​the absorbing surface and facilitates the extraction of metal minute droplets which in the absence of the stirrer is moving and the absorbing surface of the drop of metal, be formed with a stable oxide melt system such suspensions or emulsions. The use of mixers and the crucible with the coating increases the extraction of gold and silver bullion, ceteris paribus.

DETAILED DESCRIPTION OF THE INVENTION

Example 1. Starting material precipitates after cementation precipitates zinc cyanide solutions containing, wt.

  • Gold 3.5
  • Silver 2.2
  • Zinc 28.0
  • lead 7.0

in an amount of 40 kg were charged in a resistance furnace and subjected to oxidizing calcination at 800 o C for 1 h. To the impurities oxidation using oxygen or air from the line. After cooling, the precipitate was oxidized (calcine) discharged into a container and prepared by mixing the batch with calcine flyusoobrazuyuschey cryolite additive in a ratio of 1: 0.7 to the starting material, ie, in an amount of 30 kg... Then the batch was fed for smelting. The melting was carried out in an induction crucible furnace at a temperature of 1200 o C, at this temperature, the melt was maintained under continuous stirring with a stirrer for 1 hour. The crucible was used for melting furnace with an agitator, and bears on its surface of a special coating (GS Hayak Kuranov A. A. Chebykin MA Industrial products made of precious metals and alloys. metals M., 1985, pp. 140-154, 209-210).

Temperature control is carried out periodically by a thermocouple. After soaking in the melt for a predetermined time and temperature rise produced stirrer and fused slag. The remaining part, which is a noble metal melt, poured into a separate mold for ingot.

The control process performed by selecting samples at the beginning of slag melting and casting and to chemical analysis. The content of precious metals in the sediments of zinc after processing was weight.

  • Gold 0.01
  • Silver 0.14

Recovery of precious metals in ingot:

  • Gold 99.71
  • Silver 93.63

Example 2. The same conditions of the experiment, but as the batch flyusoobrazuyuschey additive is added before the melting harmless melting borax in an amount of 30 kg.

The content of zinc in the sediments after processing was, by weight.

  • Gold 0.009
  • Silver 0.1

Recovery of precious metals in ingot:

  • Gold 99.75
  • Silver 95.45

Example 3. The same conditions of the experiment, but as flyusoobrazuyuschey additive, a mixture of molten cryolite and borax in a ratio of the original draft: a mixture of 1: 0.7, ie, Cryolite 15 kg and 15 kg of borax.

The content of recycled zinc in the sediments was, by weight.

  • Gold 0.0098
  • Silver 0.12

Recovery of precious metals in ingot:

  • Gold 99.72
  • Silver 94.54

The results of the processing of lead-zinc deposits at the claimed parameters are presented in Table. 12.

Thus, the testing of the proposed method showed the possibility of efficient processing of zinc precipitation pyrometallurgical method. Compared with the known proposed method provides increased extraction of gold and silver metal ingot containing no impurity, and suitable for jewelry.

By increasing the degree of slagging on zinc and lead increases the selectivity of the process, the number of process steps and, consequently, economic costs are significantly reduced.

The developed technology can improve the ecological environment of the processing plant.

CLAIM

1. A method for processing of zinc precipitation containing precious metals, comprising calcining in an oxidizing atmosphere, melting sludge oxidized in the presence of fluxing additives to obtain molten metal, characterized in that the calcination is carried out at a temperature of 750 850 o C for 30 to 75 minutes, the oxidized product is mixed with the fluxing additives containing cryolite and / or borax in an amount providing a ratio of starting material to fluxing additive 1 (1.0 0.5) is melted at a temperature of 1100 - 1250 o C and kept under stirring for not less than 1 hour, wherein the melting is carried out in a crucible furnace with a stirrer, whose surface has a coating to provide improved wettability noble metal melt.

2. A method according to claim 1, characterized in that the additive flyusoobrazuyuschey a mixture of cryolite and borax in a ratio of 1 (0.7 0.3).

print version
Publication date 14.03.2007gg