EA031329B1 - Innovative method for refining precious metals - Google Patents

Abstract

The invention is related to the field of metallurgy of precious metals, in particular, to methods of refining precious metals. The main objective of the invention is improvement of the prior art precious metals refining. The technical result of the invention consists in increasing high-purity gold recovery from gold-containing source raw material, and in reducing the cost of conducting refining operations. Said objective is attained by provision of a method wherein a gold-containing source raw material having a silver content higher than 10% is subjected to vacuum distillation at a temperature of 1060-1350°C and a residual pressure of 10Pa, the process duration being 45-90 min; the product obtained is remelted to produce anodes for an electrochemical process in solution of aurichlorohydric acid with an excessive acidity of 200-250 g/l in terms of HCl, pure refined gold being deposited on a titanium cathode.

Description

The invention relates to the field of metallurgy of precious metals, in particular to methods of refining precious metals. The main task is to improve the known method of refining precious metals. The technical result of the invention is to increase the extraction of gold of high purity from the gold-containing raw materials, as well as reducing the cost of refining operations. This method is achieved by the fact that gold-containing raw materials with a silver content of more than 10% undergo vacuum distillation at a temperature of 1060-1350 ° C and a residual pressure of 10 ' ⁴ Pa, with a process time of 45-90 minutes, while the resulting product is melted into anodes for electrochemical process in a solution of hydrochloric acid with excess acidity on HC1 200-250 g / l with the deposition of pure refined gold on a titanium cathode.

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031329 B1

The invention relates to the field of metallurgy of precious metals, in particular to the methods of refining precious metals.

The production of refined silver always proceeds in the process of gold refining, at the moment there is only an electrochemical method of obtaining refined silver by electrolysis in a solution of silver nitrate, and therefore only methods of gold refining are considered.

There are several ways of refining precious metals, each of which has its own advantages and disadvantages.

Miller's chlorine method, in which gaseous chlorine is passed through gold-bearing raw materials, while other metals, reducing the sample of gold, are converted to highly volatile chlorides (procedure for removal efficiency: zinc, iron, antimony, tin, arsenic, copper, lead, bismuth, silver, tellurium, selenium). This method can not be used in unprepared conditions, since volatile highly toxic higher metal chlorides are formed. Moreover, the chlorine gas used in the process is extremely toxic. These poisons affect not only the worker, but also the environment. It can be used only at enterprises with special exhaust equipment, and the production cycle to obtain finished products is more than 4 days.

Chemical dissolution of gold (royal-vodka method) is based on the dissolution of the raw materials in aqua regia, in which gold goes into solution, and the contained silver precipitates in the form of its chloride.

The gold that has passed into the solution is precipitated with reducing agents to produce a precipitate in the form of powdered gold. For the implementation of this method of gold refining, a specialized aspiration system is needed, which ensures the neutralization and complete purification of flue gases formed during dissolution. The disadvantage is the need for preliminary preparation of the processed raw materials (production of granules or flakes).

The electrochemical method of refining is usually used on a production scale, when gold with a purity of at least 90% is available. Starting from the nine hundredth sample, the process of refining gives the best results (provided that silver is not more than 5%). The method consists in that the anode itself is gold itself, which is refined, and the cathode is made of gold or of very high-purity titanium. The electrolyte in this process is a solution of hydrochloric acid (HCl) and chlorine gold (AuCl ₃ ). To carry out this process, it is always necessary to have circulating gold to create the required conditions. Also, in turn, the duration of the production cycle is more than 4 days.

Known patent RU 2176279 C1 (publ. 27.11.2001. IPC C22B 11/00, C22B 7/00, C25C 1/20), which describes a method for processing secondary gold-bearing raw materials into pure gold. The method consists in the fact that in the first stage gold is deposited on the cathode after anodic dissolution in an aqueous solution of hydrochloric acid. Then, after electrolytically purification, pure gold is obtained. The disadvantage of this method is that pure gold is obtained in two stages and double consumption of electricity, chemical reagents and labor costs takes place.

The closest to the method of the invention, which is selected as a prototype, is a method of processing secondary gold alloy (RU 2516180 C1, publ. 05/20/2014. IPC C22B 11/00, C25C 1/20).

This method involves the process of electrolysis using hydrochloric acid solution of hydrochloric acid (HauCl ₄ ) with an excess acidity of HCl 70-150 g / l and the deposition of pure gold on the cathodes. Before the beginning of the electrolysis process, nitric acid is added to the electrolyte to its concentration in the electrolyte of 70-100 g / l. In the process of electrolysis, nitric acid is metered into the electrolyte, i.e. in the amount of 18-22 g of 100% nitric acid per 1 kg of the obtained cathode sediment.

The disadvantage of this method is the constant large amount of gold in work in progress in the form of electrolyte. Also, the presence of free nitric acid increases the cost of production and requires expensive structural materials for the manufacture of electrolysis baths.

Considering all the factors, an alternative method of refining precious metals is proposed, using innovative developments in the separation of metals.

In the proposed innovative method of refining precious metals, the main tasks are to increase the extraction of precious metals from gold-bearing raw materials, as well as to reduce the cost of refining operations.

The tasks are solved by using the complex technology of electrochemical refining and vacuum distillation of silver, this combination of technology belongs to the innovative methods of refining precious metals.

The use of this method of refining allows, depending on the composition of the feedstock, to use one of three directions in the general technological scheme.

So, when a significant amount of impurities and a certain content of gold and silver are contained in the raw material, the material is pre-separated by electrolysis of silver.

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With a low content of heavy impurities and a silver content of 10%, and less than 90% of gold, the feedstock, after receiving the smelting, is sent to the technology of vacuum distillation of silver, the purpose of which is the separation of gold and silver due to their physical properties.

When the gold content is from 92%, the feedstock after conducting the smelting is transferred to the manufacture of anodes for the electrolysis of gold.

Only a joint use of these areas will allow to obtain the required efficiency, as well as the absence in limiting the quality characteristics of the original gold-containing raw materials.

The use of this method in refining enterprises will allow:

1) reduce operating costs;

2) reduce the cost of finished goods;

3) reduce the duration of the production cycle;

4) reduce the amount of precious metals in work in progress;

5) reduce the natural technological and irretrievable losses;

6) reduce the amount of pollutants in the work area and in the atmosphere;

7) use innovative gold refining methods;

8) reduce the number of irretrievable losses;

9) to reduce the yield of recycled materials (slags, cakes).

The description of the current technological scheme of innovative refining of precious metals LLP Tau-Ken Altyn is shown in the drawing.

Initially, according to the technological regulations, raw materials of the following format are used as feedstock:

Dore alloy with a gold content of at least 70%, cathode gold with a gold content of at least 70%, schlich gold.

With the introduction of additional refining equipment and a change in the technological scheme, using the innovative method of refining precious metals as a raw material, it is permissible to take the following materials:

Dore alloy with gold content of 10%, cathode gold with gold content of 10%, schlich gold.

Jewelry and technical scrap.

After the acceptance of the gold-containing raw materials from suppliers, the material is sent to the fusion smelting in order to obtain a homogenized alloy. The resulting alloy after weighing, testing, depending on the content in the homogenized alloy of gold and silver, as well as the amount of impurities is sent to the following technological operations:

pre-separation, vacuum distillation, gold electrolysis.

An alloy containing a significant amount of impurities, a certain content of gold and silver is transferred to the preliminary melting workshop for the manufacture of anodes of preliminary separation by electrolysis of silver.

The alloy, having in its composition silver from 10% and gold less than 90%, as well as the absence of heavy impurities, is sent to the technological operation for the separation of gold and silver by vacuum distillation.

The alloy, having in its composition gold from 92%, is transferred to the preliminary melting workshop for the manufacture of anodes of gold electrolysis.

The pre-separation process is an electrochemical method in which the separation into separation products occurs by electrolysis in silver nitrate solution:

cathode silver with a silver content of 99.97%, anode sludge with a gold content of more than 92%, anode scrap at a rate of 20% by weight of the loaded anodes.

The impurities present in the anodes of the preliminary separation during the electrochemical reaction process are transferred to a solution of the nitric acid medium.

Since the obtained cathode silver does not comply with ST RK 933-92, it is sent to the preliminary melting shop for the manufacture of anodes for the electrolysis of silver.

The obtained crystalline cathode silver after electrolysis of silver meets its quality characteristics ST RK 933-92.

Anodic scrap after pre-separation is returned to the pre-smelting shop as a raw material for the manufacture of pre-separation anodes.

The main product of pre-separation is gold-bearing anode sludge, which serves as material for the manufacture of anodes (the average anode weight is 3-4 kg) for the electrolysis of gold.

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The process of vacuum distillation is based on the physical properties of metals, as well as their behavior in a vacuum environment.

The source material for vacuum distillation is the gold-silver alloy.

The products of the vacuum distillation process are a gold alloy with a gold content of at least 92% and silver powder with a silver content of at least 90%.

Silver powder is sent to the manufacture of anodes for the electrolysis of silver.

The gold alloy serves as a product for the manufacture of anodes for the electrolysis of gold.

The resulting anodes, made from anode pre-separation sludge, gold GVA alloy and a receiving smelting alloy with a gold content of at least 92%, are sent to the gold electrolysis shop for the electrochemical process in hydrochloric acid solution.

At the end of the process of electrolysis of gold, its products are formed in the form of: cathode gold with gold content of 99.99%, which meets the standard ST RK 933-92, silver chloride, anodic scrap in the amount of 10-15% by weight of the loaded anodes.

Silver chloride is formed due to the presence of silver in the composition of the anodes for the electrolysis of gold, which dissolves, reacts with hydrochloric acid, converts it into chloride.

The resulting silver chloride is sent to the smelting for the manufacture of anodes of electrolysis of silver.

Anodic scrap is returned to the preliminary smelting shop for the manufacture of anodes of gold electrolysis.

Washed from acid residues and dried cathode gold is transferred to the ingot casting shop for the production of finished products.

According to the principle of production of finished gold products, a similar production scheme is valid for the production of finished silver products.

Claims (1)

CLAIM The method of refining precious metals, such as gold and silver, using complex technology, which includes the following stages: manufacturing anodes for the electrolysis of gold, vacuum distillation, electrolysis of gold, characterized in that the material with gold content from 10 to 50% is sent to the manufacture of anodes with gold content up to 25%, material with gold content from 50 to 90% is sent to vacuum distillation to produce an alloy with a gold content of at least 92%, material with gold content from 90% is sent to anodes for gold electrolysis; The material selected in the first direction goes through the following stage: the anodes for the preliminary separation of silver are subjected to the process of electrolytic refining of silver to produce gold in the form of anode sludge, then by melting the anode sludge in smelting furnaces, an alloy with a gold content of at least 92% is obtained melted down for the manufacture of anodes for the electrolysis of gold; in the second direction after carrying out the process of vacuum distillation, the resulting alloy with a gold content of at least 92% is sent to the manufacture of anodes for the electrolysis of gold; the products obtained in three directions are used to obtain finished products as follows: the obtained anodes made from anodic sludge of preliminary separation, gold alloy obtained after applying vacuum distillation, and gold-containing raw materials with gold content of 90% are loaded into electrolysis baths for carrying out the electrochemical process in solution of hydrochloric acid with obtaining finished products in the form of cathode gold, while the purity of the cathode gold is 99.99%, and the parallel C., the resulting anodes of silver powder with silver content therein is not less than 90% obtained in the second direction by vacuum distillation is carried out in the electrolysis of silver silver nitrate solution to obtain the final product as a silver cathode purity 99.99%; the resulting cathode gold and cathode silver are melted into ingots that meet the quality characteristics and required standards. - 3 031329 The scheme of obtaining finished products in the form of refined gold and silver using complex technology