RU2120487C1 - Method of processing gold-containing crude - Google Patents

Abstract

FIELD: gold mining. SUBSTANCE: method is appropriate to process various types of gold- containing crude, including quartz, persistent clayey and sulfide ores. Gold-containing crude is fluoridated with ammonium difluoride and/or fluoride at crude to agent weight ratio 1:(1.2-3.5) and temperature 170-190 C. Products are heated while simultaneously removing volatile ammonium-containing fluorides, nonvolatile residue is subjected to refluoridation and water leaching to give gold- containing concentrate. EFFECT: simplified technology and enabled closed processing cycle. 6 cl, 1 dwg, 3 ex

Description

 The invention relates to methods for processing mineral ores, in particular, to the processing of a wide range of gold-containing raw materials, including refractory sulfide and clay ores, which cannot be processed by conventional methods, and can find application in the technology of gold extraction.

A widespread method for processing gold-bearing ores is cyanide leaching [R. Ripan, I. Cetianu. Inorganic chemistry M.: Mir, 1972, v. 2, p. 756 - 757]. The method is intended for processing fossilized gold, which is mainly contained in quartz ore, and has many limitations. Finely ground ore is treated with 0.03 - 0.25% solution of KCN or NaCN. Under the influence of atmospheric oxygen, gold passes into solution in the form of complex cyanide
4Au + 8NaCN + 2H ₂ O + O ₂ = 4Na [Au (CN) ₂ ] + 4NaOH
Gold is extracted from the solution with zinc chips
2Na [Au (CN) ₂ ] + Zn = 2Au + Na ₂ [Zn (CN) ₄ ]
From a gold-bearing precipitate contaminated with zinc, the latter is removed with dilute sulfuric acid. The dried residue is fused with brown or soda and cast into ingots.

 The cyanide leaching method has the following disadvantages: for technological and economic reasons, it is unacceptable for a large number of gold-bearing ores resistant to cyanide; It requires strict observance of the technological regime (concentration, pH, temperature of cyanide solutions), very fine grinding of ore (grinding costs 30 - 40% of all costs) and requires the processing of very large volumes of difficultly filtered sludge.

 Refractory gold ores are processed in other ways. One of them is a method for processing sulfide ores using nitric acid, a collective solvent of sulfide minerals, which provides for the complete opening of gold associated with them [V.V. Lodeyschikov. Extraction of gold from refractory ores and concentrates. M .: Nedra, 1968, p. 98-100].

 The disadvantages of this method include the high consumption of acid for the decomposition of ore components, the need to use acid-resistant equipment, the danger of working with concentrated acid and a large number of harmful discharges.

Максимальная степень отгонки золота в газовую фазу достигается при 900 - 10000^oC и продолжительности процесса 1,5 - 2,5 ч. Оптимальный расход натрия составляет 10 - 15% от массы исходного сырья. Выход золота в возгон составляет 97 - 99%, содержание в остатке 0,6 - 2 г/т. Последующим водным выщелачиванием хлоридных возгонов золото восстанавливается до металла, а хлориды мышьяка, железа, меди, свинца, цинка и сульфат натрия переходят в фильтрат, который подвергают переработке, представляющей собой сложный многоступенчатый гидрометаллургический передел.Closest to the claimed is a method of processing complex in composition of sulfide ores by halogenation, including treatment with sodium chloride of the source material, previously annealed in order to reduce the sulfide sulfur content to the optimal limit of 2 to 5%, which is necessary for the formation of elemental chlorine by reactions

The maximum degree of distillation of gold into the gas phase is achieved at 900 - 10000 ^o C and the duration of the process is 1.5 - 2.5 hours. The optimal sodium flow rate is 10 - 15% by weight of the feedstock. The yield of gold in the sublimation is 97 - 99%, the content in the residue is 0.6 - 2 g / t. Subsequent aqueous leaching of chloride sublimates, the gold is reduced to metal, and the chlorides of arsenic, iron, copper, lead, zinc and sodium sulfate are transferred to the filtrate, which is subjected to processing, which is a complex multi-stage hydrometallurgical redistribution.

 The total content of gold and silver chloride in the insoluble residue (cake) of water leaching is several percent, which allows you to effectively melt cake on metal crude gold [V.V. Lodeyschikov. Extraction of gold from refractory ores and concentrates. M .: Nedra, 1968, p. 96 - 98].

The disadvantages of this method is its multi-stage and complexity, including technical equipment, since the implementation of the method requires an effective system of dust, gas collection, gas purification, processing of gold chloride sublimates, as well as multi-stage processing of filtrates containing chlorides of heavy metals and arsenic. Moreover, the method is characterized by high energy intensity due to the fact that the process of chloride distillation is associated with the need to heat a large mass of ore to 90 - 1000 ^o C.

 In addition, the method is intended for a limited range of gold-containing materials, namely, for sulfide ores of complex composition.

 The objective of the invention is to simplify the method and enable closed processing of various types of gold-containing raw materials.

The problem is solved due to the fact that in the method of processing gold-containing raw materials, including halogenation, processing of halogenated products, subsequent aqueous leaching with the separation of the gold-containing fraction, halogenation is carried out by bifluoride and / or ammonium fluoride with a mass ratio of raw materials to fluorinating agent 1: 1,2 - 1: 3.5 and a temperature of 170 - 190 ^o C with the evolution of gaseous ammonia obtained fluorination products is heated at a temperature of 450 - 650 ^o C with simultaneous withdrawal of the volatile ammonium-f Oridi, and the resulting residue is subjected to repeated involatile fluorination at a weight ratio of the residue to the fluorinating agent of 1: 0.3 - 1: 0.4 and a temperature of 150 - 170 ^o C.

 The drawing shows a schematic diagram of the implementation of the method.

The method is as follows. Gold-containing raw materials are mixed with a fluorinating agent, which is taken as bifluoride and / or ammonium fluoride, in a mass ratio of 1: 1.2 - 1: 3.5 and the mixture is kept at a temperature of 170 - 190 ^o C until all minerals entering interaction with the reagent in the specified conditions. Under these conditions, minerals such as zircon, magnetite, certain types of sulfide minerals, and gold are not fluorinated.

 The mass ratio of the initial sample to the fluorinating agent is determined by the fact that when the ratio is less than 1: 1.2, incomplete fluorination and contamination of the final product with unreacted impurities are observed.

 If this ratio is higher than 1: 3.5, then the reagent overruns, which does not give an improvement in performance.

When the fluorination temperature of the ore is lower than 170 ^o C, the reaction rate is insufficient, which leads to an increase in time.

The fluorination temperature above 190 ^o C leads to the evaporation and thermal decomposition of ammonium bifluoride and the resulting fluoroammonium salts. Only within the claimed temperature range, fluorination occurs at an acceptable rate and products are formed in the form of ammonium fluoride complexes. As a gold-containing raw material, any gold-containing raw material can be used, including quartz, refractory clay and sulfide ores, or mixtures thereof.

Fe₂O₃ + 6NH₄HF₂ = 2(NH₄)3FeF₆ + 3H₂O
Al₂O₃ + 6NH₄HF₂ = 2(NH₄)3AlF₆ + 3H₂O
Фторид аммония в реакциях впрямую не участвует, поскольку при температуре фторирования руды он существует уже не в форме NH₄F, а в форме NH₄HF₂ вследствие своей термической неустойчивости.The interaction of the components that make up the gold ore with a fluorinating reagent is described by the equations:

Fe ₂ O ₃ + 6NH ₄ HF ₂ = 2 (NH ₄ ) 3FeF ₆ + 3H ₂ O
Al ₂ O ₃ + 6NH ₄ HF ₂ = 2 (NH ₄ ) 3AlF ₆ + 3H ₂ O
Ammonium fluoride is not directly involved in the reactions, since at the ore fluorination temperature it already exists not in the form of NH ₄ F, but in the form of NH ₄ HF ₂ due to its thermal instability.

 Monitoring the degree of reaction is carried out by stopping the release of ammonia and the method of x-ray phase analysis.

In an optimal embodiment of the method for a more complete separation of fine gold, part of which is associated with sulfides (mainly pyrite and arsenopyrite), the gold-containing raw materials are pre-fired in air at a temperature of 450-500 ^o C.

 For safety and economic feasibility, ammonia and water vapor transferred into the gas phase during fluorination are trapped and used later in the cycle at the stage of solution neutralization after water leaching to regenerate the fluorinating agent from the liquor.

Then the fluorinated product is subjected to heat treatment at a temperature of 450 - 650 ^o C to complete distillation of volatile ammonium fluorides (ammonium hexafluorosilicate and / or ammonium hexafluorotitanate and ammonium fluoride). Gold with other non-fluoridable minerals remains in a non-volatile residue.

Thermal processing of fluorination products (sublimation) at a temperature below 450 ^o C leads to the fact that the vapor pressure of volatile fluoroammonium salts is lower than atmospheric and therefore less than 10% of the product passes into the gas phase; moreover, titanium and iron are not separated.

Sublimation at temperatures above 650 ^o C leads to the cost of electricity without improving the performance of the method.

 It should be noted that for a more complete separation of gangue from the gold-containing fraction and the conversion of associated impurities into volatile ammonium fluorides, it is advisable to heat-treat in an inert atmosphere, which prevents the formation of non-volatile oxyfluorides, for example, titanium, tungsten, etc.

Аналогично разлагаются фтораммониевые соли марганца, хрома, вольфрама, меди.Thermal processing is carried out in a sublimation unit including a reactor, a standard fluoroplastic condenser for trapping volatile ammonium fluorides at temperatures from 150 to 270 ^o C and a fluoroplastic chip filter for trapping ammonium fluoride vapors. The latter is formed during the thermal decomposition of fluorination products such as fluoro ammonium salts of Fe, Al and some other elements of impurities that are part of the ore and form fluoro ammonium salts with a fluorinating agent. In this case, the following processes take place:

Fluorommonium salts of manganese, chromium, tungsten, and copper decompose in a similar manner.

From volatile ammonium-containing fluorides collected at a temperature of 150-270 ^° C, which depending on the type of processed raw materials may contain: ammonium hexafluorotitanate and / or ammonium hexafluorosilicate, high-purity commercial products are obtained by known methods: TiO ₂ , finely dispersed SiO ₂ and (NH ₄ ) 2SiF ₆ .

For example, in the processing of gold-containing raw materials containing titanium, volatile ammonium-containing fluorides are a mixture of ammonium hexafluorotitanate and ammonium hexafluorosilicate, from which finely dispersed TiO _{2 is} obtained when heated to 400-500 ^° C in the presence of water vapor. In other cases, volatile ammonium fluorides are (NH ₄ ) 2SiF ₆ , which can be used as a commercial product itself, or it can be used to obtain amorphous finely dispersed SiO ₂ when neutralizing ammonium hexafluorosilicate solutions with ammonia.

который затем возвращают на стадию галогенирования.The NH ₄ F collected on the filter is then used to regenerate the fluorinating agent by reaction

which is then returned to the halogenation step.

The non-volatile residue after sublimation, containing magnetic, zircon, iron, aluminum fluorides and impurities of other fluorides, as well as gold, is subjected to repeated treatment with ammonium bifluoride and / or ammonium fluoride in a mass ratio of the feed to the fluorinating agent equal to 1: 0.3 - 1: 0 , 4, and a temperature of 150 - 170 ^o C with the aim of the formation of fluoroammonium salts.

 The mass ratio of the non-volatile residue to the fluorinating agent upon repeated fluorination of less than 1: 0.3 does not ensure the complete transition of fluorides to soluble hexafluoroammonium salts and thereby leads to contamination of the final product with iron and aluminum salts.

 The ratio of these substances more than 1: 0.4 leads to inappropriate consumption of a fluorinating agent without improving process parameters.

Lowering the temperature of re-fluorination below 150 ^o C leads to a decrease in the reaction rate and an increase in the viscosity of the system due to the reagent melt.

Raising the temperature of re-fluorination above 170 ^o C leads to the cost of electricity without improving the performance of the method.

 The re-fluorinated product is subjected to aqueous leaching to dissolve the fluoro ammonium salts of iron and aluminum and separate them from the insoluble gold-containing fraction.

The resulting leach solution containing soluble fluoroammonium salts is neutralized, for which purpose the ammonia water collected in the fluorination step is used. The hydroxides of iron, manganese, aluminum and other impurity metals formed during the neutralization of the leach solution after drying are calcined at a temperature of 600 - 700 ^o C and as a result a marketable product is obtained - red doped pigment (ocher, minium).

 The gold-containing precipitate separated from the leaching solution is washed, dried and crude gold is obtained, to some extent associated with non-fluorinated minerals, the separation of gold from which can be carried out by known non-chemical methods well developed for placer gold.

 For example, if zircon and magnetite are present in the feed, the precipitate is subjected to magnetic separation to separate magnetite from the gold-bearing residue. Gold is concentrated in a non-magnetic fraction - zircon. Its content in this case is 900 - 1000 g / t, and in magnetite - below 2 g / t. Thus, the extraction of gold into the non-magnetic fraction is 96 - 98%.

Elemental gold from zircon can be extracted by smelting (t _pl. Au = 1063 ^o C, t _pl. ZrSiO ₄ = 2490 ^o C), or by washing zircon sand (d Au = 19.3 g / cm ³ , d ZrSiO ₄ = 4 , 5 g / cm ³ ), or in another known manner.

 In other cases, the gold-containing precipitate obtained after leaching is sent for re-melting.

 After smelting gold from zirconium or extracting it by other known methods, the latter can be used in foundry to obtain molding mixtures and casting coatings, as well as enamels and glazes of sintered refractories.

 During the processing of quartz-clay gold-silver-containing ores, the gold content in the solids is 100 - 120 kg / t (and silver - 500 kg / t). The total content of gold and silver compounds in the concentrate is more than 60%, which makes gold smelting a highly effective process. Gold and silver recovery reaches 99.8 - 99.9%. In this processing method, silver does not act as a gold depressant, as in cyanidation.

 The simplest case is the processing of purely quartz gold-bearing ores (not related to refractory). The gold content in the residue is 900 - 950 kg / t, the recovery is at a level of ≈ 100%.

The difference between the proposed method for processing gold-containing raw materials from the known one consists in the use of ammonium bifluoride and / or fluoride as a halogenating agent, as a result of which the gold during halogenation remains in a non-fluorinated solid residue (in the known method, the gold goes into chloride sublimation during halogenation). This determines the differences in the subsequent stages of processing and provides when implementing the proposed method a new technical result, which consists in the following:
- in contrast to the known methods aimed at processing a certain type of gold-containing raw materials, the proposed method is universal, suitable for processing any gold-containing raw materials using one reagent,
- significantly simplifies the method by reducing the number of stages of processing and reducing the volumes involved in the processes of solutions.

In addition, the method has the following additional advantages:
- provides almost 100% turnover of the halogenating agent,
- the method allows to obtain additionally such high-class commercial products as titanium dioxide of a high degree of frequency, finely divided silica, freeze-dried silicon hexafluorosilicate of high purity and doped iron oxide (ocher, minium),
- the proposed method is closed and environmentally friendly at all stages.

 For the implementation of the method using known, technically simple and affordable equipment.

 The method is illustrated by the following examples.

 Example 1

Sample No. 1 according to x-ray phase analysis is a mixture of ilmenite FeTiO ₃ , magnetite Fe ₃ O ₄ , pyrite FeS ₂ , zircon ZrSiO ₄ , amphiboles X _2-3 Y ₅ Z ₈ O ₂₂ (O, OH, F, Cl) ₂ , where X = Ca, Na, K; Y = Mg, Cr, Li, Fe ²⁺ , Fe ³⁺ , Mn, Al; Z = Si, Al, Ti, and traces of mica. A feature of this ore is the presence in it of fine, up to 50 microns, and bound in gold aggregates, which cannot be extracted by conventional methods. The gold content in the original ore is 21.2 g / t.

300 g of ore are annealed in a porcelain cup at a temperature of 470 ^° C for 2 hours to convert pyrite, with which thin gold is partially associated, into hematite.

The resulting product in an amount of 293.2 g is mixed with 390 g of ammonium bifluoride ammonium technical TU 6-08-283-74 (ratio 1: 1.3). The mixture is placed in a glass graphite reactor and heated in an electric furnace at a temperature of 180 ^° C. for 20 hours. The resulting product is a loose mass of gray and, according to X-ray diffraction analysis, is a mixture of (NH ₄ ) 2TiF ₆ , (NH ₄ ) 3FeF ₆ , (NH ₄ ) 3AlF ₆ , ZrSiO ₄ and magnetite.

A profiled product in an amount of 610 g is placed in a nickel evaporator for sublimation of (NH ₄ ) 2TiF ₆ and incubated for 40 minutes at a temperature of 550 ^o C. The collected sublimate in an amount of 183 g is processed into TiO _{2 in a} known manner with the regeneration of ammonium bifluoride. Gold according to neutron activation analysis in a sublimated product is completely absent.

A non-volatile residue in an amount of 256 g with a gold content of 24.8 g / t is mixed with 90 g of ammonium fluoride-ammonium bifluoride (ratio 1: 0.35) and heated in a glass-carbon reactor at a temperature of 170 ^o C for 1 h to transfer iron fluorides, aluminum and other non-volatile fluorides in ammonium fluoride salts.

 The re-fluorinated product in an amount of 345 g is subjected to water leaching of 1725 ml of water to transfer all soluble salts to the filtrate. The operation is repeated three times for complete purification of the precipitate from ammonium fluoride salts.

The resulting precipitate (cake) is dried at a temperature of 90 - 110 ^o C, its mass is 57 g, the gold content is 111 g / t. No gold was found in the filtrate.

 Then the cake is subjected to magnetic separation on an electromagnetic single-roller separator brand 738 TSEM with a magnetic field of 1400 e. The resulting magnetic fraction in an amount of 50.6 g contains 1.6 g / t of gold, and a non-magnetic fraction in an amount of 6.4 g contains 970 g / t of gold. Extraction of gold in the non-magnetic fraction is 97.6%.

 Example 2

 Sample No. 2 consists of fragments of quartz (up to 80%), tuff with quartz-limonite veins and a small amount (10 - 12%) of clay material, which dramatically affects the filterability of the pulp and greatly complicates the process of separation of gold-containing solutions during cyanidation. A feature of this ore is the presence in it of a large amount of native silver, as well as silver in the form of sulfide and sulfide-arsenic minerals. The gold content in the original ore is 160 g / t.

300 g of ore are mixed with 870 g of ammonium bifluoride ammonium technical TU 6-08-283-74 (ratio 1: 2.9). The mixture is placed in a glass graphite reactor and heated in an electric furnace at a temperature of 190 ^° C. for 15 hours. The product obtained is a loose mass of gray color and, according to an X-ray phase analysis, is a mixture of (NH ₄ ) 2SiF ₆ , (NH ₄ ) 2FeF ₆ and (NH ₄ ) 3AlF ₆ .

A profiled product in an amount of 905 g is placed in a nickel evaporator for sublimation of (NH ₄ ) 2SiF ₆ and incubated for 1 h at a temperature of 600 ^o C. The collected sublimation of (NH ₄ ) 2SiF ₆ in an amount of 710 g is processed into SiO _{2 in a} known manner with regeneration ammonium bifluoride. Gold according to neutron activation analysis in the sublimated product is completely absent.

A non-volatile residue in an amount of 90 g with a gold content of 532 g / t is mixed with 36 g of ammonium fluoride-ammonium bifluoride (1: 0.4 ratio) and heated in a glass-carbon reactor at a temperature of 170 ^o C for 1 h to transfer iron, aluminum and other non-volatile fluorides of impurities in ammonium fluoride salts.

 Re-fluorinated product in an amount of 125 g is subjected to aqueous leaching of 625 ml of water to transfer to the filtrate all soluble salts. The operation is repeated three times to completely clean the insoluble precipitate.

The resulting precipitate is dried at a temperature of 90 - 110 ^o C, its mass is 0.41 g, the gold content is 117 kg / t, the silver content is 500 kg / t. No gold was found in the filtrate. Gold recovery was 99.9%.

 Example 3

Sample No. 3 is a typical quartz gold-bearing ore (SiO ₂ 95%) with a small admixture of sulfide and oxidized iron minerals, including the so-called “rusty” gold. The gold content in the original ore is 6.9 g / t.

300 g of ore are mixed with 1050 g of ammonium bifluoride-ammonium technical TU 6-08-283-74 (ratio 1: 3.5). The mixture is placed in a glass-graphite reactor and heated in an electric furnace at a temperature of 190 ^o C for 15 hours. The resulting product is a loose mass of gray color and according to x-ray phase analysis is a mixture of (NH ₄ ) 2SiF ₆ and (NH ₄ ) 3FeF ₆ .

A profiled product in an amount of 1040 g is placed in a nickel evaporator for sublimation of (NH ₄ ) 2SiF ₆ and incubated for 1 h at a temperature of 600 ^o C. The collected sublimation of (NH ₄ ) 2SiF ₆ in an amount of 845 g is processed into SiO _{2 in a} known manner with regeneration ammonium bifluoride. Gold according to neutron activation analysis in the sublimated product is absent.

A non-volatile residue in an amount of 21 g with a gold content of 98 g / t is mixed with 8.4 g of ammonium fluoride-ammonium bifluoride (1: 0.4 ratio) and heated in a glass-carbon reactor at a temperature of 170 ^° C. for 45 minutes to transfer iron fluoride to ammonium fluoride salt.

 The re-fluorinated product in an amount of 29 g is subjected to water leaching of 145 ml of water to transfer the fluoro ammonium salt of iron to the filtrate. The operation is repeated several times until the insoluble precipitate (cake) is completely cleaned.

The resulting precipitate is dried at a temperature of 90 - 110 ^o C, its mass is 0.0023 g, the gold content is 900 kg / t. No gold was found in the filtrate. Gold recovery is 99.9%.

Claims (6)

1. A method of processing gold-containing raw materials, including halogenation by heating, processing of halogenated products and water leaching, followed by separation of the gold-containing fraction, characterized in that the halogenation is carried out by bifluoride and / or ammonium fluoride with a mass ratio of raw materials to fluorinating agent 1: 1,2 - 1: 3.5 and a temperature of 170 - 190 ^o C with the evolution of gaseous ammonia, processing fluorination products is carried out by heating at a temperature of 450 - 650 ^o C with simultaneous withdrawal of volatile ammoniysode fluoride-containing, and the resulting non-volatile residue containing gold, is subjected to halogenation repeated at a weight ratio of the residue to bifluoride and / or ammonium fluoride of 1: 0.3 - 1: 0.4 T at 150 - 170 ^o C. 2. The method according to p. 1 characterized in that the gold-containing raw materials are preliminarily fired at a temperature of 650 - 750 ^o C.  3. The method according to p. 1, characterized in that the ammonium fluoride formed during the thermal processing of fluorination products is returned to the halogenation stage.  4. The method according to p. 1, characterized in that the processing of fluorination products of gold-containing raw materials is carried out in an inert atmosphere.  5. The method of claim 1, characterized in that the solution after aqueous leaching is neutralized with ammonia from the halogenation step.  6. The method according to PP. 1 and 5, characterized in that the ammonium fluoride formed in the neutralization step is returned to the halogenation step.