Extraction method of precious metals from ores and concentrates

FIELD: metallurgy.

SUBSTANCE: method involves processing of base material during heating in water vapour atmosphere and further leaching of precious metals from processing product in solutions of reagents. Besides, processing of base material is performed in water vapour atmosphere, which is mixed with oxygen at the temperature of 300-500°C at oxygen content in gas mixture within 10-20%. Waste gases released during the processing are brought into contact with the solution that is combined with a leaching solution.

EFFECT: decrease of temperature and reduction of costs at preparation of refractory ores and concentrates to leaching.

1 tbl, 1 ex

 

The invention relates to the metallurgy of noble metals and, in particular, to a method for the hydrometallurgical extraction of metals from technologically resistant materials, for example from carbonaceous ores and concentrates. The proposed method can be used when conducting analyses, as well as when conducting geochemical, geological prospecting and exploration, the revaluation of balance sheet and off-balance-sheet reserves in natural and anthropogenic raw materials.

The vast majority of minerals of noble metals consists of crystalline and amorphous inorganic and organic components. In favorable cases, the noble metals may be present in the raw material matrix in the form of discrete metal particles or embedded in the structure of certain minerals-carriers. This raw material does not pose technological challenges for industry and analysis.

In many kinds of ores and concentrates gold and platinum metals are in the form of separate nuclei, subatomic size of the clusters and clusters that are chemically or physically associated with the surrounding condensed inorganic and organic matter matrix. This scattering removing any elements of the matrix raw material is exceptionally difficult task. For example, to technologically resistant types of gold-what about the raw materials include granite, clay, metamorphic schists, gneisses, in particular carbon, black Sands, graphite, and many others. In these rocks, especially carbon can contain significant amounts of noble metals dispersed in the matrix. They are difficult to extract with conventional processing methods cyanidation. In numerous publications emphasize that organic compounds of gold and platinum do not dissolve in cyanide solutions and remain in the tailings leach.

The most common methods of processing of refractory ores and concentrates include a preliminary physical disintegration of dry or wet way to technically and economically viable particle size of at least 0.1 and 0.01 mm, This operation allows to partially expose the incorporation of noble metals in the matrix in the form of native or intermetallic particles having a size of not less than 0.001 mm. smaller gold particles can be separated from the matrix of raw material and extracted the next step in the reaction solution only after further chemical disintegration of hard particles in the matrix material. For this resistant raw materials after physical grinding is subjected to thermo-chemical, chemical, or more complex processing. For example, resistant raw material is subjected to oxidative Obi who have at 500-1000°C with subsequent leaching of precious metals from cinder ([1] Malinetskii I.N., Chugaev L.G. metals precious metals. - M.: metallurgy, 1987. - 366 C.). Type of training concentrates to cyanidation is roasting in the presence of lime or other calcium-containing materials ([2] RF Patent №2078146 from 27.04.1997), which solves the problem of disposal of sulphurous gases.

In these ways unproductive components of the matrix raw material ruin, and precious metals are transferred into the solution, concentrate, and further isolated from them marketable product by known methods.

None of the known methods of industrial (not laboratory) chemical treatment agents fail to achieve the desired fullness of the opening thrust of the matrix raw material or its permeability sufficient for oxidizers, complexing agents or extractants, which could ensure the maximum extraction of rare metals. In this regard, a significant portion of valuable metals is lost with tails leaching, resulting in lower economic and ecological efficiency of production. The most radical approach is melting refractory concentrates on lead, copper or other alloy with subsequent allocation of a noble metal known methods [1].

Pyrometallurgical processing of hard materials, including including oxidative roasting or smelting order is Elektrownia noble metals copper, lead or other metals, inevitably accompanied by a loss "micron particles of gold and platinum with dusts and gaseous products.

The closest in technical essence and the achieved effect is a method for processing gold ores and concentrates (RF Patent No. 2309187 from 27.10.2007), including firing in an atmosphere of water vapor at a temperature in the furnace 700-900°C. shredded raw materials are placed in an oven and heated in a steam atmosphere. In these conditions, the matrix raw material is destroyed, in particular in the gas phase passes sulphur and arsenic, and the noble metal microparticles fully opened for further cyanidation. If the feedstock contains organic carbon, as practice shows, in an atmosphere of steam he also decompose. The product steam treatment is subjected to leaching in solutions of reagents. In particular, leaching the product of firing in cyanide solutions was uneventful.

However, gaseous products specified reactions and sulfur gases carry away the released particles of noble metals and carry them out of the candle. Subsequent recovery of gold from waste sulfur-containing gas products and dusts significantly complicates the process.

The basis of the invention is to simplify the preparation of refractory concentrates first of all what about the carbon, to cyanide leaching with the exception of losses of noble metals. In particular, the aim is to reduce the temperature and relative costs in the processing of raw materials steam.

This technical result is achieved by the fact that the roasting of the concentrates of lead in the atmosphere of water vapor and oxygen at a temperature of 300-500°C, and the content of oxygen in the source gas mixture is maintained within the range of 10-20%, while exhaust gases are brought into contact with the solution, which is used in the leaching.

The proposed method is chemical-thermal destruction of the organic matrix, as an integral part of the carbonaceous ores and concentrates of precious metals, to improve the efficiency of subsequent leaching.

The process according to the method of the prototype at temperatures above 700°C also allows you to destroy the organic structure, but in such conditions the oxidation of sulfide sulfur, accompanied by release of large amounts of sulfur dioxide and arsenic; oxides of iron and non-ferrous metals. Both conditions have a negative impact on the feasibility process indicators: the high cost of steam superheat, for recycling and cleaning gases, gases, and particles of noble metals in varying degrees escaped pestiviruses films - extraction with cyanide is reduced.

Chorus what do you know, what mineral forms of carbon and organic compounds, primarily graphite, very stable in the air. In the atmosphere water vapor without oxygen oxidation of carbon by reaction

in accordance with thermodynamic calculations starts at 650°C.

Thermodynamic calculations show that in the presence of oxygen, oxidation of carbon

should take place in the entire temperature range. The results of the experiments revealed that the oxidation of carbonaceous substances in the composition of gold-bearing concentrates in the atmosphere of water vapor and air begins at a temperature of 250-270°C. the Rate of decomposition of organic matter, which is acceptable for practical use of this method, is achieved at temperatures above 300°C. it is Noteworthy that under combined action of steam and oxygen, the oxidation of sulfides is developed starting with only 600°C.

On the rate of oxidation of organic matter significantly affects the content of oxygen in the source gas mixture. In real-world devices (steam generator) steam generated by evaporation of water in closed and sealed containers. To conserve energy during subsequent overheating and maintaining high temperature steam seek to prevent its dilution air. Virtually content free KIS is oroda in the gas mixture, supplied to the processing of concentrates due to the "suction" of the air, may be 1-2%. As experience has shown, at temperatures from 300 to 600°C this amount of oxygen is insufficient for activation of the process according to reaction (2). And only when the oxygen content of 10-12% in the specified temperature range the intensive oxidation and decomposition of carbonaceous substances of mineral concentrates. Processing of carbonaceous concentrates at temperatures over 600°C additional effect does not, in the presence of the processed raw materials sulphides begins intensive oxidation of sulfides that are not always justified. More than 20%, the oxygen content in the initial mixture does not give a positive effect. In this regard, the optimal composition of the gas mixture is air, by volume diluted in 1.5-2 times the ferry.

As a result of oxidation of organic carbon particles of metallic gold are released for subsequent leaching. It is established that organic compounds of gold when destroyed, the gold is recovered to a metallic state, i.e. enters cinerea form.

However, microparticles of gold present in the raw material is initially formed during the decomposition of organic matter ("dust" gold), when the steam treatment can be carried away from the reactor leaving gas-vapor mixture. Pairs vannoy system is a good extractor of gold, not allowing to settle him on the walls of the flue. Particulate noble metal vapor-gas mixture, it is advisable to bring into contact with water or with special catching solutions, for example, by bubbling. A similar approach is proposed for the recovery of gold from flue gases produced by the combustion of coal (Patent RF №2249054 from 27.03.2005). In this way as catching gold you can use technical working solution used to leach gold from the products of processing of concentrates steam. Precious metals move in the solution and then extracted with known methods in the primary process.

Implementation of the proposed method are discussed in the following examples.

The original gold-bearing sulphide (pyrite) concentrate contained 37 g/t gold, 85 g/t silver, 43% sulfide sulfur and 1.1% organic carbon. The carbon in accordance with the data of IR spectroscopy was presented betuloides and organic forms. Collectively, the properties exhibited by concentrate cyanidation processes, it can be classified as resistant. Direct cyanidation of the concentrate allows you to extract in a solution of gold is not more than 47%, silver by 29%.

Sample carbonaceous gold-bearing concentrate a mass of 200 g order thermochemical opening the ash is before cyanidation was subjected to processing in a current of superheated steam in a laboratory setup. To this concentrate was placed on a porous membrane in a vertically placed tubular furnace with an electric heater. Heating to a predetermined temperature, was carried out with control using homoalanine thermocouple junction which was placed directly into the volume of the concentrate. Automatic temperature control was carried out by a microprocessor-based single-channel power meter-regulator TRM1 on PI-law.

Source pair was sealed container of water, heated to a temperature of intense boiling and connected to the reactor steaming. Pairs of bottom-up pass through the layer and concentrate on hot pipe received in the container catching solution. Excessive steam pressure in the working area corresponded to the depth of immersion of the exhaust pipe in catching solution and 0.005 MPa. Steam consumption and processing time (1 hour) all experiments were identical.

For introduction into the initial mixture of oxygen directly into periodogram part of the furnace filed the air (in experiments 4 and 5 - oxygen-air mixture). The oxygen content in the air-steam mixture in contact with the sample, was calculated taking into account the costs of steam, air, the pressure in the reaction zone and the set temperature on the known dependencies.

After steaming and cooling gap is placed in the sample concentrate was subjected to leaching in a reactor with mechanical stirrer (laboratory photomachine) cyanide solution (1 g/l NaCN, the pH of 10.3, W:T=2:1, duration 24 hours). After leaching, the slurry was filtered, the cake washed, determined the content of gold and silver in solution and in the solid residue. Taking into account the received digits expected recovery of gold.

Experience 6 held under the terms of the prototype: in the oven served only steam and heated the sample up to 750°C

Catching pairs of solutions were analyzed for gold content. In experiment 7 for the preparation of leach solution used a solution obtained by trapping the pair on stage steaming the original sample. The results of the experiments are presented in table 1. The solutions obtained by trapping method prototype was acidic in nature due to the formation of sulfur and sulfuric acid. Such solutions can be used for the preparation of barren cyanide solution is impossible. For the extraction of gold from them requires independent technology.

Table 1
The results of the experiments
no experienceTemperature steaming, °CThe oxygen content in the mixture, %Extraction into solution, % The loss of gold tails, %Gold extracted in catching solution, %
AuAgAuAu
125055837420
2300107964192
3400158569132
4500208772103
560025857196
6 prototype 750Did not expect8073128
The acidic solution
7450158371132

Comparative analysis of the known technical solutions, including fashion, selected as a prototype, and the present invention allows to conclude that the aggregate of the stated characteristics are provided by the perceived achievement of the technical result. Implementation of the proposed technical solution makes it possible to increase the recovery of gold from carbonaceous concentrates in commodity solutions at 3-5% and to reduce the cost of handling concentrates.

The method of extracting precious metals from ores and concentrates, including processing of source material when heated in the atmosphere of water vapor and subsequent leaching of precious metals from product processing reagents, wherein processing the source material is carried out in an atmosphere of water vapor mixed with oxygen at a temperature of 300-500°C, and the content of the oxygen in the gas mixture is maintained within the range of 10-20%, and waste in the processing of gases is brought into contact with the solution, which is combined with the leaching solution.



 

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FIELD: metallurgy.

SUBSTANCE: method involves solid-phase roasting of wastes mixed with soda to fix arsenic to a water-soluble form of sodium arsenate. Then, water leaching and deposition from arsenic solution is performed. In order to obtained the product from water leaching with low residual arsenic content of 0.7%, solid-phase roasting is performed at 850°C so that a roasted product containing 2.9% of arsenic is obtained. Water leaching of the roasted product is performed with extraction degree of 84%. Deposition from arsenic solution is performed in the form of arsenic sulphide with sodium sulphide at pH=3 with deposition degree of 99.6%, and filtrate with arsenic content of 0.02 g/l for removal of residual amount of arsenic by neutralisation and deposition with iron compounds meets the requirements of sanitary norms.

EFFECT: obtaining low-toxicity commodity product of arsenic sulphide and product of water leaching with low residual content of arsenic.

1 dwg, 1 tbl, 5 ex

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EFFECT: increasing the efficiency of the process cycle at reduction of costs and emission of hazardous gases.

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FIELD: mining.

SUBSTANCE: method of bath-well leaching of metals from ores includes treatment of mineral mass by solution of leaching in baths and metal winning from product solution. Baths are formed along leached mass, in the baths bottom a system of injection and extraction wells is built located above the level of bath with depth not less than the lower point of leached layer of mineral mass, and baths are filled with agglomerated mineral mass or pulp prepared in advance from extracted material, mineral mass in baths is treated by solution of leaching, and metal is extracted from product solution. Reusable solution obtained after metal extraction is strengthened or replaced with solution of another composition and is supplied to the system of injection wells for leaching of lower layers of material, then working solution is pumped off with leached metal through the system of extraction wells and metal is extracted from it; for leaching of lower layers of material solutions of environmentally safe chemicals, such as chlorides or thiosulfates, are used.

EFFECT: invention allows improving metal extraction efficiency.

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SUBSTANCE: invention can be used in the technology of obtaining the compounds of rare-earth metals at complex processing of apatites, and namely for obtaining of concentrate of rare-earth metals (REM) from phosphogypsum. Method involves sorption of rare-earth metals. At that, prior to sorption, phosphogypsum is crushed in water so that pulp is obtained in the ratio Solid : Liquid=1:(5-10). Sorption is performed by introducing to the obtained pulp of sorbent containing sulphate and phosphate functional groups, at the ratio of Solid : Sorbent=1:(5-10) and mixing during 3-6 h.

EFFECT: increasing REM extraction degree to finished product.

5 tbl, 5 ex

FIELD: metallurgy.

SUBSTANCE: method involves leaching of cadmium from raw material in solution of sodium ethylene diamine tetraacetate with its further extraction from solution and regeneration of ethylene diamine tetraacetate. Cadmium leaching is performed in two stages. The solution obtained at the first stage is supplied for extraction of cadmium, and residue of the first stage is supplied to the second cadmium leaching stage. The solution obtained at the second stage is used for leaching of cadmium from raw material at the first stage. Besides, leaching at the second stage is performed in presence of hydrogen peroxide at maintaining its concentration in the range of 10-15 g/dm3 during 2-2.5 hours.

EFFECT: increasing cadmium extraction degree.

2 tbl, 2 ex

FIELD: metallurgy.

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3 cl, 4 tbl, 1 ex

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5 cl, 9 tbl, 6 ex

FIELD: metallurgy.

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FIELD: metallurgy.

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FIELD: metallurgy.

SUBSTANCE: reduction is performed with hydrogen generated in solution; at that, reduction is catalysed with reduced metal itself, which is contained in finely dispersed state. Reduction process is performed in multi-pass reactor at variable pressure that is changed with frequency of 1-5 Hz from maximum to minimum values of 8 kg/cm2 to 0.25 kg/cm2. Extraction plant of metals capable of hydrogen absorption from solutions includes dosing device, modified displacement pump, electrolyser for hydrogen generation and multi-pass reactor in the form of labyrinth.

EFFECT: simplifying the process and improving the purity of extracted metal.

10 cl, 9 dwg, 8 tbl, 4 ex

FIELD: metallurgy.

SUBSTANCE: method includes drying of an industrial massif of stale tailings of upstream impoundments. Then the thickness of tailings is divided into non-productive strata including lean tailings from the upper part of the industrial massif, not exposed to hypergene changes, and productive strata from the base of the industrial massif enriched with gold and formed in the process of hypergene conversion. Then the circuit of the hypergene converted stratum is established. Afterwards tailings of upper non-productive strata are removed, and tailings of hypergene converted strata are processed. Processing is carried out by leaching with gold extraction. Gold extraction from tailings of hypergene converted productive strata is carried out with cyanidation.

EFFECT: invention provides for growth of gold production in sufficiently short periods due to simplified process cycle and reduction of time for preparation of secondary raw materials for processing.

3 cl, 1 tbl, 1 ex

FIELD: metallurgy.

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13 cl, 3 ex

FIELD: metallurgy.

SUBSTANCE: method involves solid-phase roasting of wastes mixed with soda to fix arsenic to a water-soluble form of sodium arsenate. Then, water leaching and deposition from arsenic solution is performed. In order to obtained the product from water leaching with low residual arsenic content of 0.7%, solid-phase roasting is performed at 850°C so that a roasted product containing 2.9% of arsenic is obtained. Water leaching of the roasted product is performed with extraction degree of 84%. Deposition from arsenic solution is performed in the form of arsenic sulphide with sodium sulphide at pH=3 with deposition degree of 99.6%, and filtrate with arsenic content of 0.02 g/l for removal of residual amount of arsenic by neutralisation and deposition with iron compounds meets the requirements of sanitary norms.

EFFECT: obtaining low-toxicity commodity product of arsenic sulphide and product of water leaching with low residual content of arsenic.

1 dwg, 1 tbl, 5 ex

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