RU2256712C1 - Method of reprocessing of primary gold-sulfide ores - Google Patents

Abstract

FIELD: mining and metallurgy industry.

SUBSTANCE: the invention is pertaining to the field of mining and metallurgy industry and may be used for extraction of gold from gold-sulfide ores of a different mineral composition. The method provides for a coarse breaking of ore, its fine crushing with grading, flotation concentration, bacterial leaching of sulfide flotation concentrate, neutralization of products of bacterial leaching of a sulfide flotation concentrate, a sorption leaching of the neutralized products of bacterial leaching of a sulfide flotation concentrate, joint sorption leaching of tailings of the sorption leaching of the neutralized products of the bacterial leaching of a sulfide flotation concentrate and flotation tailings, a desorption of gold from a saturated sorbent, electrolytic reduction of gold from eluates, smelting of the cathode deposits onto a bullion of Dore alloy. The bacterial leaching of sulfide flotation concentrate is conducted a stage by stage at the temperature of 37-45°C using different communities of bacteria at each stage, with temperature rise on the last stages. Neutralization of the products of the bacterial leaching of the sulfide flotation concentrate is conducted at aeration of the pulp by a compressed air, and after the aeration they conduct an oxidation of the pulp by oxygen and its cyanidation hardening. The sorption leaching of the neutralized products of the bacterial leaching of the sulfide flotation concentrate conduct at the fractional dosing of cyanide. The technical result of the invention is an increased extraction of gold at a decreased consumption of cyanide.

EFFECT: the invention ensures an increased extraction of gold at a decreased consumption of cyanide.

5 cl, 3 dwg, 5 tbl, 1 ex

Description

The invention relates to the mining industry and can be used in the processing of minerals for the extraction of gold from primary gold sulfide ores, in which small particles of gold are dispersed in sulfide minerals, represented mainly by pyrite, arsenopyrite, pyrrhotite, as well as antimonite, with a small amount of galena, sphalerite and chalcopyrite, and are not available for dissolution by cyanides.

Pyrometallurgical processes (roasting, smelting), autoclave leaching, and bacterial leaching are used to open finely dispersed gold from sulfide minerals in industry. The advantages of bacterial leaching over these processes are the absence of dust and gas emissions, lower capital and operating costs, and high temperatures and pressures are not required.

A known method for the extraction of precious metals from refractory gold-arsenic ores, including the stage of bacterial oxidation and the subsequent dissolution of gold using chlorine, hypochlorites or thiourea (GB patent No. 2180829, 1987.).

There is also known a method of separating gold from arsenopyrite ores, involving the biooxidation of sulfides and cyanide leaching of gold (US patent No. 4822413, 1989). However, these methods are not economical enough, and the degree of gold recovery is not high enough.

Known are technologies employing BIOX ^R processes (Dew, DW, et al. The BlOX ^R process for biooxidanion of goldbearing ores of concentrates. Biomining: Theory, Microbes and Industrial processes, ed. DERawlings, Chapter 3. Berlin: Springer-Verlag, 1997 ) and You Tech (Miller P.C. The desing and operating practice of bacterial oxidation plant using moderate thermophilles (the You Tech process). Biomining: Theory, Microbes and Industrial processes, ed. DERawlings, Chapter 4. Berlin: Springer-Verlag , 1997) for the biooxidation of sulfide concentrates obtained by the processing of refractory gold-arsenic ores.

A method of processing ores using these processes includes ore preparation, beneficiation (gravitational with flotation or only flotation), biooxidation of the concentrate obtained, separation of bacterial solutions from solid biooxidation residues in which gold and silver are concentrated, neutralization of solutions in two stages using limestone in the first stage , lime in the second stage, sorption cyanidation of solid biooxidation products, metal desorption and regeneration of the sorbent returned to the process I, electrolysis gold-containing solution and melt-eluate cathodic precipitation to obtain an alloy of gold and silver - dore.

The main disadvantages of this method are: increased yield of concentrates (up to 15%) directed to bacterial oxidation, which leads to the need to increase the volume of bioreactors, the consumption of reagents and, ultimately, leads to an increase in costs and the cost of ore processing; increased consumption of sulfuric acid to maintain pulp pH in optimal limits during biooxidation of concentrates with a high content of carbonates and pyrrhotite with an increase in pulp volume, high consumption of reagents (cyanide) for cyanidation; the presence of an expensive system of separation of solid from liquid in biooxidation products (decantation operations in thickeners), and the inevitable loss of fine gold with suspensions in the thickeners plums.

A known method of processing gold and silver ores, including grinding, gravity and / or flotation concentration, bacterial leaching and cyanidation, which is carried out before bacterial leaching, and bacterial leaching cakes are flotated together with the original ore or concentration products (RF patent No. 2023734, class .22 V 11/00, 11/08, publ. 11/30/1994).

The disadvantage of this method is its low profitability and incomplete extraction of gold.

Closest to the proposed method for processing gold sulfide ore is a method for processing sulfide ores, including coarse crushing of ore, its grinding with classification, flotation concentration, bacterial leaching of sulfide flotation concentrate, neutralization of products of bacterial leaching of sulfide flotation concentrate, sorption leaching, concentration-free leaching leaching of sorption tailings method of treating neutralized products of bacterial leaching of sulfide flotation concentrate and flotation tailings, desorption of gold from a saturated sorbent, electrolytic separation of gold from eluates, smelting of cathode deposits on an ingot of Dore alloy (RF patent No. 2234544, class C 22 V11 / 08, C 22 V 3/18 publ. 2004.08.20). According to him, bacterial leaching is carried out in two stages at a temperature of 34-36 ° C with the pulp turning from the second stage to the first, and the pulp of bacterial leaching products after two-stage neutralization is directed to sorption leaching.

The main disadvantage of the closest analogue is the relatively low recovery of gold from sulfide ore for a number of reasons:

insufficiently complete oxidation of sulfide and elemental sulfur generated during bacterial leaching (up to 4-5.5%), due to the reduced number of stages, which during the subsequent sorption leaching operation sharply increases the cyanide consumption as a result of the formation of rhodanides and worsens the process of gold sorption, since thiocyanates are desorbents of cyanide complexes with ion-exchange resins;

neutralization of flotation tails leads to strong foaming due to the presence of flotation reagents in the pulp and the release of carbon dioxide, which leads to a deterioration in the distribution of sorbent in the pulp and disruption of the sorption process;

salts of heavy metals dissolved during bacterial leaching precipitate upon neutralization, and then dissolve upon interaction with cyanide, increasing its consumption and also worsen the sorption of gold, reducing its recovery.

The objective of the invention is to increase the efficiency of the processing of refractory sulfide ores.

The technical result achieved by the invention is to increase the completeness of the extraction of gold while reducing the consumption of cyanide.

The technical result is achieved by the method of processing primary gold sulfide refractory ores, including large-scale crushing of ore, its refinement with classification, flotation concentration to obtain sulfide flotation concentrate and tailings, bacterial leaching, sulfide flotation concentrate, neutralization of bacterial leaching products, sorption leaching leaching leaching neutralized products and tailings flotation about enrichment, desorption of gold from a saturated sorbent, electrolytic separation of gold from eluates, smelting of cathode deposits on an ingot of Dore alloy, according to the invention, bacterial leaching of sulfide flotation concentrate is carried out in stages at a temperature of 37-45 ° C, using different bacterial communities at each stage, s by increasing the temperature in the last stages, the neutralization of the products of bacterial leaching of sulfide flotation concentrate is carried out during aeration of the pulp with compressed air, and after aeration oxidation of the pulp with oxygen and its cyanidation are carried out, while the sorption leaching of neutralized products is carried out with fractional supply of cyanide.

This set of features contains features, each of which is necessary to achieve the claimed technical result in all cases of using the invention for which the scope of legal protection is claimed.

In particular cases of use, the invention is characterized in that cyanidation and sorption leaching of the neutralized products of the bacterial leaching of sulfide flotation concentrate is carried out when the pulp is saturated with oxygen 10 mg / m ³ .

And also the fact that aeration of the pulp with compressed air is carried out with a specific air flow rate of 0.5 m ³ / m ³ .

In addition, the sorption leaching of the neutralized products of the bacterial leaching of the sulfide flotation concentrate is carried out while maintaining the concentration of cyanide in the liquid phase of the pulp at the level of 300 mg / l.

And finally, the fact that the oxidation of the pulp with oxygen is carried out with saturation up to 20 mg / m ³ .

In refractory sulfide raw materials, gold is in a finely dispersed state, enters into the structure of sulfide grains and can be extracted only after the destruction of this structure. The opening of finely disseminated gold during bacterial leaching is carried out by a community of bacteria. Along with the widespread iron-oxidizing microorganisms (Thiobacillus ferrooxidans), other types of bacteria are also used. In the oxidation of pyrrhotite-containing gold-arsenic concentrates, both the association of iron and sulfide-oxidizing bacteria T.ferrooxidans, Leptospirillum ferrooxidans, Sulfobacillus thermosulfidooxidans and Ferroplasma asidiphilum, and sulfur-oxidizing bacteria (Thiobacillus thioox) are used.

The emerging bacterial communities depend on the temperature at which the bioprocess is conducted. Iron-oxidizing bacteria actively develop at a temperature of 26-30 ° C and pH = 1.5-2.0. At higher temperatures of about 45 ° C, thermophilic community bacteria are dominant, including Thiobacillus caldis (oxidizes S °) and L.ferrooxidans (oxidizes Fe ²⁺ ).

The oxidation process takes place in the system “medium (electrolyte) - mineral” and is carried out according to the laws of electrochemical corrosion. Bacteria oxidize Fe ²⁺ to Fe ³⁺ , and the resulting elemental sulfur to sulfuric acid. Bacteria primarily oxidize sulfides with lower electrode potential. For example, in a mixture of pyrrhotite-arsenopyrite-pyrite, pyrrhotine is most actively oxidized, then arsenopyrite and pyrite are the most difficult [Karavayko G.I. et al. Biohydrometallurgy of gold and silver, “Non-ferrous metals”. 2000. No. 8].

Therefore, it is important when carrying out the process of bacterial leaching of a sulfide concentrate containing a mixture of sulfides in order to more fully oxidize them, to have a sufficient number of stages to ensure the temperature regime and the optimal species composition of bacteria for each stage of the process.

The proposed temperature regime of 37-45 ° C with increasing temperature in the last stages allows to achieve a high degree of sulfide oxidation to 96-98% and reduce the residual elemental sulfur content from 4-5.5% to 1-1.5%.

During bacterial leaching, as proposed in the closest analogue (BIOS method), a community of bacteria is formed that actively oxidizes mainly pyrrhotite and arsenopyrite without affecting pyrite and elemental sulfur.

Whereas in the claimed method, the maximum reduction in the content of sulfide component in the solid phase is achieved already in the apparatus of the first stage, from 18% to 6.3-7.8%. The formation of elemental sulfur peaks in the first two stages to 4.35% and only then begins to decline, reaching 1.62% in the fourth stage.

The effect of rhodanide ion on gold recovery was investigated by studying the sorption leaching of products of bacterial leaching of flotation concentrates. The composition of the liquid phase of the tail pulp is given in table 1.

Table 1 The concentration of NaCN, g / l The concentration in the liquid phase, mg / l Au Fe Cu Zn Ni CNS ^- 0.5 3.3 131.2 10.5 0.8 1,5 10600 1,0 4.3 355.0 14.5 1.9 2,8 14200 3.0 5.3 680.0 13.8 3.4 2,5 47800

High concentrations of rhodanide ion are the result of incomplete oxidation of sulfide and elemental sulfur at the stage of bacterial leaching, which led to the presence of intermediate valencies in the sorbent redistribution material and sulfur compounds that react with cyanide to form rhodanide ion:

CN ^1- + S ⁰ = CNS ^1-

The effect of the thiocyanate ion on the sorption of gold is shown in Table 2. As can be seen from the above data, rhodanide ion, even at low concentrations, has a noticeable negative effect. Thus at a concentration CNS ^1- 2,3 g / l of capacity of the resin is reduced by 3 times.

table 2 Brand of anion exchange resin Concentrate walkie-talkie in the liquid phase, mg / l Gold Capacity, mg / g Au Fe CNS AM-2B 6.2 0.3 10.0 17.90 6.2 0.3 200,0 13.82 6.2 0.3 2300.0 5.71

Studies on pulp aeration during the process of neutralization and liming showed in all cases a positive effect. As can be seen from Table 3, the sorption leaching of gold after neutralization and active air mixing of the pulp occurs with a lower consumption of sodium cyanide and better indicators for the extraction of gold and the composition of the liquid phase of the pulp - the concentration of rhodanide ion is 20-30% lower.

Table 3 Process characteristic Sorption leaching of gold Duration, hour NaCN consumption, kg / t Au _W , g / t Liquid phase, mg / l Au CNS ^- No air 6 18.9 19.6 3.9 7900 With air 6 16.8 12.6 7.9 5300

The solid phase of the neutralized biooxidation products contains significant amounts of secondary precipitates of heavy metal hydroxides, residual undecomposed sulfides, elemental sulfur and other products, which, when cyanated in alkaline media, dissolve well with the formation of cyanide and rhodanide complexes. The content of rhodanide ion reaches 6-12 g / l. All this leads to an excessive consumption of sodium cyanide, a decrease in the resin capacity for gold due to the occurrence of competing sorption, a decrease in the extraction of gold from the liquid and solid phases, and a slowdown of the process.

Before cyanidation, the pulp is pre-oxidized with oxygen with a saturation of 20 mg / m ³ in order to reduce the amount of cyanide-absorbing substances, improve pulp composition and increase gold recovery by sorption leaching, and cyanidation and sorption leaching processes are carried out with oxygen saturation of 10 mg / m ³ . The preliminary oxidation of the pulp with oxygen with a saturation degree of 20 mg / m ³ makes it possible to stabilize the ionic composition of the pulp, reduce the amount of cyanide absorbers, improve the dissolution of gold in the solid phase and the process of sorption of gold from the liquid phase, and ultimately reduce the gold content in the tailings and increase the recovery gold from ore. The content of thiocyanate in the pulp is reduced by more than 2 times, the consumption of sodium cyanide is reduced by 2.5 times, the gold content in the tailings is reduced by 2.4 times, the extraction increases by more than 20% (Table 4).

Table 4 Process characteristic Time hour Indicators of sorption leaching Gold content in solid. tails phase, g / t The gold content in the liquid. tail phase, mg / l The concentration of CNS ^- in the liquid phase of the tailings, g / l NaCN consumption, kg / t Gold recovery,% With air 2 2.2 0.71 1,2 11.1 65 With oxygen 2 0.8 0.3 0.5 4.3 87

Fractional supply of cyanide to the process of sorption leaching of neutralized products of bacterial leaching of sulfide flotation concentrate can reduce the initial concentration of cyanide in the head apparatus and, accordingly, reduce the consumption of cyanide for side reactions with cyan-absorbing substances. Instead of supplying the necessary amount of cyanide to the head units and creating an initial concentration of 400-500 mg / l (as in the prototype), a fractional supply of cyanide is used on the sorption leaching of neutralized products of bacterial leaching of sulfide flotation concentrate through the process steps while maintaining a low concentration of cyanide in the pulp liquid phase at the level of 300 mg / l. This allows to reduce the consumption of cyanide for the formation of by-products by 1.5 times and improve the conditions of gold sorption (Table 5).

Table 5 Sorption Leaching Conditions Indicators The concentration of NaCN, g / l Duration, hour Au content in cake, g / t CNS concentration ^- in the liquid phase NaCN consumption, kg / t 0.2 6 3,54 1,11 4.3 1,0 6 2.92 3.83 11.1 5,0 6 1.93 9.7 38.1

The invention is illustrated by drawings, where Fig. 1 shows a graph of the behavior of sulfide sulfur in the solid phase of a pulp during biooxidation, Fig. 2 shows a graph of the behavior of elemental sulfur in a solid phase of a pulp during biooxidation, Fig. 3 shows a circuit diagram of apparatuses providing the claimed method of processing sulfide ores.

A method of processing sulfide ores is as follows.

Example

Ore from the quarry or from the ore warehouse by dump trucks is fed into the receiving hopper 1 of the crusher of large crushing. Coarse crushing is carried out to a particle size of 300-400 mm. Coarse ore conveyors 2 through the intermediate hopper 3 is fed to grinding.

Grinding is carried out in two stages on the same line. The first grinding stage is carried out in a semi-self-grinding mill 4 operating in an open cycle. The second grinding stage is in a ball mill 5, operating in a closed cycle with hydrocyclones 6. The upper discharge of hydrocyclones with a particle size of 85-90% CL-0.074 mm is sent to sulfide flotation.

Flotation is performed in pneumatic machines in one stage with two flotation concentrates 7. Sulphide floc concentrate is sent for bacterial leaching, and flotation tailings after thickening in radial thickeners 8 are sent for sorption leaching.

Bacterial leaching of sulfide flotation concentrate is carried out in four stages at a temperature of 37-45 ° C in cascades of pneumomechanical devices 9 equipped with heat exchangers to remove heat generated during oxidation. At the same time, different bacterial communities are used at each stage. The process is carried out with increasing temperature at stages 3 and 4 with a decrease in elemental sulfur content to 1-1.5%. This allows to achieve a more complete oxidation of sulfides and reduce the elemental sulfur content from 4-5.5% to 1%.

The maximum decrease in the content of sulfide component in the solid phase is achieved already in the apparatus of the first stage, from 18% to 6.3-7.8% and a slight slight decrease in the subsequent ones. The formation of elemental sulfur reaches a maximum in the first two stages to 4.35% and only then begins to decrease, reaching 1.62% in the fourth stage (see figures 1 and 2).

Further, the oxidized concentrate is supplied for neutralization. When neutralizing and liming the pulp of bacterial leaching, an intensive aeration of the pulp is carried out with compressed air with a specific air flow rate of 0.5 m ³ / m ³ and adjusting the alkalinity of the pulp to pH = 11-12. An additional flow of oxygen prevents the foaming of the pulp, which further improves the cyanidation process .

The oxidized concentrate, in the form of slightly sulfuric pulp, after neutralization and aeration in the cascade of pneumomechanical devices 10, is sent to preliminary oxidation with oxygen in the cascade of devices 11 with mechanical stirring and saturation up to 20 mg / m ³ to reduce the amount of cyan-absorbing substances and stabilize the ionic composition of the pulp. This leads to an increase in gold recovery during sorption leaching, reduces the number of cyanide absorbers and, as a result, reduces their consumption by 4-6 times.

The neutralized pulp treated with oxygen is supplied for preliminary cyanidation to the cascade of apparatuses 12, and then it enters the cascade of sorption leach apparatuses of the neutralized products of bacterial leaching of sulfide flotation concentrate (sorption-1). For leaching, sodium cyanide is used, which is fed in a fractional dosage along the steps of the cascade, maintaining a concentration of 300 mg / l, in order to reduce the consumption of cyanide for the formation of harmful side substances that interfere with the sorption process, and to maintain a constant concentration in the process.

Sorption is carried out on an anion exchange resin in a countercurrent mode: sorbent pulp. Cyanidation and sorption leaching of the neutralized products of bacterial leaching of sulfide flotation concentrate is carried out when the pulp is saturated with oxygen 10 mg / m ³ .

Joint sorption leaching of the sorption leaching tailings of the neutralized products of the bacterial leaching of sulfide flotation concentrate and flotation tailings (sorption-2) is carried out in tower units 13 with plates arranged in several parallel lines.

Sorption-1 and sorption-2 are carried out separately. Tails of sorption-1 can be directed to the head of sorption-2. Tails of sorption after neutralization from residual cyanide by calcium hypochlorite in a cascade of apparatuses with mixing devices 14 are discharged into the tailings pond. The saturated anion-exchange resin from the head apparatuses of both sorption is separated from the pulp and sent to desorption and regeneration.

Gold desorption is carried out by thiourea sulfate solutions. The regeneration of saturated resin is carried out in column apparatuses with 15 solutions of sulfuric acid and sodium alkali. The regenerated resin is returned to sorption, and the gold-containing regenerates are sent to electrolysis.

The electrolytic separation of gold from the eluates is carried out in electrolyzers with steel cathodes 16. The cathode deposits (gold-containing sludge) are filtered off and after drying and firing are sent to the smelting.

Melting is carried out in induction furnaces 16. The final products are gold bullion (Dore alloy), which are sent for refining to another enterprise.

Thus, the inventive method allows to increase the completeness of the extraction of gold and reduce the consumption of cyanide in the processing of refractory sulfide ores, which ultimately leads to increased efficiency of the process. Through gold recovery from refractory sulfide ore with a gold grade of 3.5 g / t increases to 90.4%, and from ore with a grade of 5.04 g / t (analog) to 96.1 g / t.

Claims (5)

1. A method of processing primary gold sulfide refractory ores, including large-scale crushing of ore, its grinding with classification, flotation concentration to obtain sulfide flotation concentrate and tailings, bacterial leaching of sulfide flotation concentrate, neutralization of bacterial leaching products, sorption leaching, neutralization of neutralized neutralized products products and tailings of flotation concentration, gold desorption from us saturated sorbent, electrolytic separation of gold from eluates, smelting of cathode deposits on an ingot of Dore alloy, characterized in that the bacterial leaching of sulfide flotation concentrate is carried out stepwise at a temperature of 37-45 ° C using different bacterial communities at each stage, with an increase in temperature in the last stages, the neutralization of the products of bacterial leaching of sulfide flotation concentrate is carried out during aeration of the pulp with compressed air, and after aeration, the pulp is oxidized with oxygen and cyanidation, while sorption leaching of neutralized products is carried out with a fractional supply of cyanide. 2. The method according to claim 1, characterized in that the planning and sorption leaching of neutralized products is carried out when the pulp is saturated with oxygen 10 mg / m ³ . 3. The method according to claim 1, characterized in that the aeration of the pulp with compressed air is carried out with a specific air flow rate of 0.5 m ³ / m ³ . 4. The method according to claim 1, characterized in that the sorption leaching of neutralized products is carried out while maintaining the concentration of cyanide in the liquid phase of the pulp at a level of 300 mg / L. 5. The method according to claim 1, characterized in that the oxidation of the pulp with oxygen is carried out with saturation up to 20 mg / m ³ .

Images