RU2538435C2 - Removal method of gold from refractory ores by heap leaching - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to hydrometallurgy of precious metals and can be used namely for removal of gold at heap leaching of refractory gold-containing ores with cyanide solutions. The method consists in the fact that pyrite cinders are added to the ore prior to laying into a pile or during its formation. Eroded, aged cinders and cinders of current production are used as pyrite cinders. After formation of a pile, leaching of gold with solutions of cyanides is performed.

EFFECT: improving a degree of gold removal at cyanide leaching of refractory ores; reducing consumption of cyanide.

8 cl, 6 tbl, 6 ex

Description

The invention relates to the field of hydrometallurgy of precious metals and can be used, in particular, for the extraction of gold by heap leaching of refractory sulfide gold-bearing ores with cyanide solutions.

A known method of leaching (MA Meretukov, AM Orlov. Metallurgy of precious metals, (foreign experience). M: Metallurgy. S.97-113. 1991). The method includes crushing the ore, preparing the ore for stacking, laying the stack on a waterproofed and environmentally sound foundation, installing a heap irrigation system and supplying the cyanide solution in air with mechanical sprinklers, sprayers from rubber tubes.

The disadvantage of this method is the low efficiency of the extraction of gold from the stack.

A known method of heap leaching of gold, including crushing ore, pelletizing ore with the introduction of cement and an aqueous solution of sodium cyanide, laying a stack on a waterproofing base, installing an irrigation system, supplying an oxygenated solution by irrigation and obtaining production solutions (See. "Heap leaching of noble metals". / / Under the editorship of Prof. Doctor of Engineering M.I. Fazlullin. - M.: Publishing House of the Academy of Mining Sciences. 2001. S. 471-473). Gold recovery after 60 days of leaching was 80-85% under conditions of additional introduction of sodium cyanide into the circulating solutions in the leaching stage.

The disadvantage of this method is the low dissolution rate of gold, not allowing during the summer period to use one base for leaching 2-3 ore stacks on it. Due to the long leaching stage, poorly soluble salts accumulate in the circulating solutions, leading to the formation of sludge in pipelines. In order to prevent precipitation, a special reagent is introduced, which increases the cost of maintenance.

A known method (patent SU 1669193) of a four-stage chemical leaching of non-ferrous metals from pyrite cinder by successive leaching with a solution of sulfuric acid with the addition of iron scrap, filing a soda solution to neutralize at elevated temperature, calcining the precipitate and leaching the calcined precipitate with a hydrochloric acid solution of gold thiocarbamide.

Known patent RU 2379363 "Method of ore preparation of oxidized gold-bearing ores for heap leaching of gold." The method includes sieving the ore, grinding, re-sieving, crushing, sieving, re-crushing and sieving, then mix the ore with a binder containing cement in an amount of 30-50 kg / t of ore, moisten up to 12% moisture, granulate and form a heap from the obtained pellets for leaching gold. As a binder with stirring, a mixture of cement and self-decaying ferro-slag is used, which makes up 30-50% of the total amount of the mixture. Ferro-slag has the following composition,%: Cr ₂ O ₃ - 5.5-6.5; SiO ₂ - 24.5-26.5; CaO 46-48; Al ₂ O ₃ - 4.0-5.0; MgO - 13.5-14.5; moisture - 0.5-1.1. The use of cement and self-dissolving ferro-slag as a binder mixture makes it possible to reduce the amount of cement used, increasing the efficiency of the method.

Known patent RU 2430170 "Method for the extraction of gold from oxidized clay gold-bearing ores", which includes crushing, sifting ore, mixing the ore with a binder, granulating the ore to obtain pellets, forming a stack of the obtained pellets and heap leaching of gold by irrigation with sodium cyanide solution to obtain gold-fortified solutions. As a binder, a co-grinding product of a mixture containing 70% of blast furnace granulated slag and 30% of lime in terms of active CaO taken in the amount of 25 kilograms per ton of ore is used. The size of the ore crushing is 60 mm, and the product of co-grinding of a mixture consisting of blast furnace granulated slag and lime has a fineness of grinding corresponding to a specific surface of 3000-3500 cm ² / g.

The closest in technical essence to the claimed method of heap leaching of gold from refractory sulfide ores is the method according to patent RU 2430170 "Method for the extraction of gold from oxidized clay gold-bearing ores", which includes crushing, sifting ore, mixing ore with a binder, granulating ore to obtain pellets , the formation of a stack of the obtained pellets and heap leaching of gold by irrigation with a solution of sodium cyanide to obtain solutions enriched in gold solutions. As a binder, a co-grinding product of a mixture containing 70% of blast furnace granulated slag and 30% of lime in terms of active CaO taken in the amount of 25 kilograms per ton of ore is used. The size of the ore crushing is 60 mm, and the product of co-grinding of a mixture consisting of blast furnace granulated slag and lime has a fineness of grinding corresponding to a specific surface of 3000-3500 cm ² / g.

The disadvantage of this method is the increased fineness of ore crushing, which, when refractory ores are mined, reduces the degree of gold recovery due to the length of the leaching process. The problem to which the invention is directed, is to develop a method of heap leaching of gold from refractory sulfide ores containing, in particular, sulfides and carbonates.

The technical result of the proposed technical solution is to increase the degree of gold extraction during cyanide leaching of refractory sulfide ores, reducing the consumption of cyanide, and also replacing part of the cement with mechanically activated pyrite cinder.

The technical result is achieved by the fact that pyrite cinders are introduced into the ore before stacking or during the formation of the stack, followed by leaching of gold with a cyanide solution. At the same time, according to the preference of use, pyrite cinders are arranged in a row: weathered, stale, cinders of current production (current).

The method provides that before stacking the ore and pyrite cinders are mixed in the presence of cement, moisturize, drench and stand, and stacking is carried out over time, while the pellets retain ductility.

According to a variant of the method, in the process of stack formation, pyrite cinders are stacked in layers, and the thickness of their layer should not impair the filtration properties of the ore stack piled to be mined.

In the case of using stale and current pyrite cinder, they are aerated for a time determined experimentally. In addition, it is possible to use current pyrite cinder as an additional binder after mechanical activation in planetary mills or in other similar devices after grinding in the -0.044 mm class.

The choice of pyrite cinders as an additive to gold-bearing refractory sulfide ore is due to the following.

1. Pyrite cinders are an additional source of gold and silver mining: the gold content varies in the range of 0.5-3.0, silver - 2.0-30.0 g / t. Such gold and silver contents allow their cost-effective leaching with a high degree of recovery.

2. The presence of sulfur compounds in pyrite cinders during their oxidation and storage contributes to the formation of sulfuric acid, the content of which increases with storage time. During the formation of the ore stack in the presence of pyrite cinder and its aging, the carbonate component of the ore decomposes, which contributes to the release of gold from the "carbonate shirt" and its subsequent dissolution by cyanides. The resulting calcium sulfate aggregates small ore particles, prevents premature destruction of pellets and prevents contamination of production solutions, which, in turn, contributes to a sufficiently high filtration permeability of the ore stack during mining.

3. The presence of elevated levels of sulfide and sulfate sulfur in pyrite cinders, in contrast to blast furnace, copper, nickel slag, with prolonged contact with atmospheric oxygen also contributes to the formation of sulfur compounds of variable valence: HS ^- , S ₂ O ₃ ^2- , SO ₃ ^{2 -} , which are complexing agents in the presence of which the dissolution of gold occurs (G.G. Mineev, A.F. Panchenko - Solvents of gold and silver in hydrometallurgy. M: Metallurgy. 1994, p. 73-82). An increased concentration of such compounds is noted in weathered cinders, which are most preferred. When using stale and current pyrite cinders, their additional aeration is necessary.

4. The reduced salt content in the cinders of the current production allows them to be used after mechanical activation in planetary mills or other similar equipment as an additional binder simultaneously with cement, which reduces the consumption of the latter. The required fineness of grinding pyrite cinder, as shown by preliminary experiments, should be at least -0.044 mm. An option to further reduce cement consumption during the formation of pellets is the addition of lime during grinding of pyrite cinders, the flow rate of which is determined during experimental work.

The proposed method is as follows.

An impenetrable base is constructed at the work site and an ore pile to be leached is formed on it. To this end, ore is crushed and sieved, weathered pyrite cinders or stale or current pyrite cinders are introduced into it after aeration, moisten, granulate, pellet the ore and pellets are laid, and stacking is carried out over time while the pellets maintain ductility. The aeration time when using stale or current pyrite cinders is established experimentally. Aeration is necessary to generate sulfuric acid and sulfur ions of variable valency: HS ^- , S ₂ O ₃ ^2- , SO ₃ ^2- , - which are complexing agents when gold is dissolved.

According to another variant of the method, pyrite cinders are poured in layers during the formation of the ore stack in an amount that does not impair the filtering permeability of the stack being constructed. The number of layers and their power depend on the technological properties of ore and pyrite cinder, which is established in the process of conducting pilot works.

Weathered pyrite cinders having a minimum sulfide sulfur content and increased sulfur concentrations of lower oxidation levels are most preferred. In addition, in such cinders, the pH reaches values of 2-3, which contributes to the dissolution of the "carbonate shirt" of gold particles and their release for cyanide leaching. The resulting calcium sulfate contributes to the cementation of small classes of ore, thereby increasing the stability of the pellets and preserving the filtering ability of the ore stack.

In turn, stale and especially current cinder, when used, must be subjected to additional aeration with air, which increases the concentration of complexing agents in them, which contribute to the dissolution of gold.

To reduce cement consumption during the formation of pellets, it is possible to use current cinders after mechanical activation. A variant of this technique is the additional introduction of lime during the mechanical activation of pyrite cinder.

Mechanical activation is carried out in planetary mills or other similar devices, allowing to grind pyrite cinder in the class of -0.044 mm.

As experimental work has shown, pyrite cinders, crushed by mechanical activation in the -0.044 mm class, begin to exhibit gripping properties and, when rolling ore, can partially serve as a replacement for cement, reducing its consumption. The additional introduction of lime during the mechanical activation of pyrite cinders enhances their gripping properties. Lime consumption is determined in preliminary experiments. The grasping properties of mechanically activated pyrite cinders are preserved for one hour, during which they must be mixed with ore and cement, which is carried out in a continuous process of granulation and pelletizing.

It was established by experimental work that the optimum amount of introduced pyrite cinder is 20-25% of the mass of leached ore. When the ore content is less than 20% of pyrite cinders, the required degree of decomposition of the "carbonate shirt" of gold-containing carbonate ore is not achieved, and when the ore contains more than 25% of cinder, the specific consumption of cyanides increases due to the interaction of acid-soluble iron with cyanides.

The possibility of implementing the proposed technical solution is illustrated by the following examples.

The feasibility of using pyrite cinders for heap leaching of refractory sulfide ores is illustrated by examples 1 and 2.

Example 1

To weighed samples of refractory gold-bearing ore (ore - metasomatites according to composition diorites,%: SiO ₂ - 65.0; S - 3.0; Fe - 6.5; CO ₂ - 5.3) weathered pyrite cinder composition,%: 51.2 Fe ₂ O ₃ ; 10.4 FeO; 2.0 S; 7.5 SiO ₂ ; 2.9 Al ₂ O ₃ ; 1.9 CaO; 3.0 MgO; 1.4 g / t Au - in the amount of 10, 15, 20, 25, 30% by weight of ore and cement at the rate of 15 kg / t. The mixture was stirred, moistened, dipped and stood for 5 days. Pellets were loaded into the percolator and spent cyanide leaching with a solution of sodium cyanide 1.06 g / DM ³ . Leaching indicators are shown in table 1.

Table 1 Dependence of leaching indicators on the content of pyrite cinders introduced into ore Indicators % pyrite cinder According to the prototype method 10 fifteen twenty 25 thirty The mass of the mixture, g 52900 55400 58120 61110 663010 49260 Au content, g / t 1.78 1.81 1,69 1.83 1.88 1,57 Au content in solution, mg / dm ³ 0.58 0.62 0.62 0.69 0.67 0.36 Cyanide consumption, kg / g Au 0.76 0.78 0.83 0.89 1,08 1.17 Au recovery,% 65,4 68.3 73,2 75.3 77.8 46.2

As can be seen from the data in table 1, the gold recovery in the presence of weathered pyrite cinder is significantly higher than in the prototype method. In this case, the optimum content of cinder in the ore is in the range of 20–25% by weight of the ore.

Example 2

To weighed samples of refractory gold-bearing ore (ore — terrigenous-carbonate rocks of the composition,%: SiO ₂ - 59.6; S - 2.7; Fe - 7.3; CO ₂ - 9.6) weathered pyrite cinder of the composition according to example 1 in the amount of 10, 15, 20, 25, 30% by weight of ore and cement at the rate of 15 kg / t. The mixture was stirred, moistened, dipped and stood for 5 days. Pellets were loaded into the percolator and spent cyanide leaching with a solution of sodium cyanide 1.06 g / DM ³ . Leaching indicators are shown in table 2.

table 2 Dependence of leaching indicators on the content of pyrite cinders introduced into ore Indicators % pyrite cinder According to the prototype method 10 fifteen twenty 25 thirty The mass of the mixture, g 52890 55980 58660 62790 69950 56540 Au content, g / t 3.79 3,55 3,51 3.72 3.73 3,55 Au content in solution, mg / dm ³ 0.81 0.83 0.83 0.91 0.98 0.70 Cyanide consumption kg / g Au 1.32 1.33 1.35 1.24 1.01 1.49 Au recovery,% 41.8 43,2 44.6 50.3 64.3 36.8

As can be seen from the data in table 2, the extraction of gold from terrigenous-carbonate rocks in the presence of weathered pyrite cinder is also higher than in the prototype method. In this case, the optimal content of cinder in the ore is in the range of 25-30% by weight of the ore.

Similar results were obtained when pyrite cinders were introduced in the process of pouring ore stacks from pellets not containing pyrite cinders on various types of gold ore.

The preference for the use of pyrite cinders depending on the time of their aging during storage is illustrated in Example 3.

Example 3

5 kg of weathered, stale and current pyrite cinders were added to samples of 20 kg each of refractory gold sulphide ore in Example 1, cement was introduced at the rate of 15 kg per 1 ton, respectively. After preparation and aging of the pellets for 5 days, cyanide leaching was carried out according to Example 1. The leaching indicators are shown in table 3.

Table 3 Choosing the preferred use of pyrite cinder Indicators Type of cinder weathered stale current The mass of pellets, kg 25 25 25 The content of Au in the pellets, g / t 1.83 1.80 1.72 The Au content in solution, mg / dm ³ 0.74 0.65 0.49 Cyanide consumption, kg / g Au 0.95 1.00 1.15 Au recovery,% 81.4 76,2 50.6

As can be seen from the data in Table 3, according to the degree of extraction of gold from ore and the specific consumption of sodium cyanide, pyrite cinders are ranked according to preference of use: weathered> stale> current. Similar results were obtained with the leaching of terrigenous-carbonate gold-bearing ores.

The effectiveness of aeration by air of stale and current pyrite cinders is illustrated in Example 4.

Example 4. Through moist stale and current pyrite cinder containing 3 and 5% sulfide sulfur, respectively, air was passed for 20 days. At the end of aeration, pyrite cinders were mixed respectively with refractory sulfide ore at the rate of 25% of the ore mass in the presence of cement in Example 1 and leached in the same manner as in Example 1. Under similar conditions, pellets were prepared using non-aerated pyrite cinders and leached. Leaching indicators are shown in table 4.

Table 4 The effect of aeration on the degree of gold recovery and specific consumption of cyanide Indicators Pyrite cinder stale current source aerated source aerated The mass of pellets, kg 25 25 25 25 Au content in pellets, g / t 2.80 2.80 2.72 2.72 Au content in 1.06 1.14 0.68 0.73 solution, mg / dm ³ Cyanide consumption 1,0 0.96 1.15 1,02 kg / g Au Au recovery,% 76,2 82.3 50.6 53.6

As can be seen from the data in table 4, additional aeration of the stale and current pyrite cinders contributes to an increase in the degree of gold recovery and a decrease in the specific consumption of sodium cyanide. Similar results were obtained with the leaching of terrigenous-carbonate gold-bearing ores.

The influence of the aging time of the pellets formed in the presence of pyrite cinder on the degree of gold recovery and the specific consumption of sodium cyanide is illustrated in Example 5.

Example 5. The pellets formed in Example 1, containing 25% pyrite cinder, were divided into 2 parts: one part immediately after the pelletizing was placed in a percolator and leaching started, and the leaching of the second part began after standing for 5 days. Leaching indicators are shown in table 5.

Table 5 The influence of the aging time on the strength of the pellets and leaching rates Indicators Pellets without standing after standing The strength of the pellets, MPa 0.2 0.6 The mass of pellets, kg 25 25 The content of Au in the pellets, g / t 1.86 1.86 The Au content in solution, mg / dm ³ 0.63 0.66 Cyanide consumption, kg / g Au 1,02 0.93 Au recovery,% 68.5 71.3

As can be seen from the data of table 5, the maturation of the formed pellets before stacking them in a stack helps to increase strength, the degree of extraction and reduce the specific consumption of sodium cyanide.

The possibility of using pyrite cinders of the current production after mechanical activation as an additional binder is illustrated in Example 6.

Example 6. Pyrite cinder of the current production was crushed in a planetary mill in the class -0.044 mm, introduced into cement and the mixture was used as a binder to obtain pellets in Example 1. After standing for 5 days, the strength of the obtained pellets was determined by the standard method. The determination results are shown in table 6.

Table 6 The dependence of the strength of the pellets on the composition of the binder The composition of the pellets Consumption, kg / t Cement fifteen fourteen 13 12 eleven 10 Cinder - one 2 3 four 5 Strength, MPa 0.6 0.5 0.5 0.4 0.4 0.2

As experiments have shown, the additional introduction of calcium oxide increases the strength of the pellets by 15%.

Similar results were obtained using ore in example 2.

Thus, the above examples show the advantages and feasibility of the proposed method for heap leaching of gold from refractory sulfide ores.

Claims (7)

1. The method of heap leaching of gold from refractory sulfide ores, including the construction of an impenetrable base at the place of work, crushing, sieving the ore, mixing the ore with a binder, granulating the ore with pellets and forming a stack, installing leaching irrigation systems and collecting production solutions, characterized the fact that pyrite cinders are introduced into the ore before stacking or during its formation, followed by leaching of gold with cyanide solutions. 2. The method according to claim 1, characterized in that the pyrite cinder contains gold and silver. 3. The method according to claim 1, characterized in that before stacking the ore and pyrite cinders are mixed, a binder is introduced, which is cement, moistened, doused and aged, and stacking is carried out for a time that preserves the ductility of the pellets . 4. The method according to claim 1, characterized in that when forming the stack, pyrite cinders are stacked in layers with a layer thickness that does not impair the filtration properties of the ore stack. 5. The method according to claim 1, characterized in that during the formation of the stack, pyrite cinder is arranged in the following row: weathered, stale, cinder of the current production. 6. The method according to claim 5, characterized in that before using the stale and current production of pyrite cinders, they are pre-aerated. 7. The method according to claim 5, characterized in that when using pyrite cinder of the current production, they are pre-crushed in the class of -0.044 mm and used as an additional binder.