Method for extracting gold from low-grade gold sulfide ore by heap leaching

Abstract

The invention relates to the field of metallurgy and chemical engineering, in particular to a heap leaching gold extraction method for low-grade gold sulfide ore. Comprising the following steps that an anti-seepage bottom mat is laid on a dump leaching site; pre-treating the sulfide gold ore by using quick lime; ore crushing; ore is poured and piled on the upper portion of the bottom pad; spraying is conducted on the top of the ore heap and a side slope frame pipe, the gold-containing pregnant solution is collected, and the spraying solution is a sodium cyanide solution; and recovering gold from the gold-containing pregnant solution. According to the heap leaching gold extraction method provided by the invention, the quicklime is adopted to carry out pretreatment (iron removal, desulfurization and arsenic removal) on the sulfide gold ore, and then processes of subsequent ore crushing, heap building, spraying, adsorption and the like are carried out, so that the difficult problems of heap leaching utilization and popularization of low-grade sulfide ore resources are solved.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a heap leaching method for extracting gold from low-grade sulfide gold ore. Background Technology

[0002] Heap leaching process (such as) Figure 1 (As shown) Heap leaching is a method that uses a leaching solution to spray onto a ore heap, selectively leaching the valuable components from the ore during the downward seepage process, and recovering the valuable components from the precious solution flowing out from the bottom of the heap. Due to its advantages of simple process, low equipment investment, and low operating cost, heap leaching is commonly used in the mining of copper, uranium, gold, and silver mines, as well as in the treatment of tailings from beneficiation plants and smelter slag containing valuable components. It is mainly applied to the treatment of fine-grained, low-grade oxide ores. However, sulfide ores, due to the presence of iron, sulfur, arsenic, and other factors that negatively impact the heap leaching process, are not suitable for this process. Traditional methods for treating sulfide ores involve flotation and gravity separation to extract gold, which are costly and require high-grade feedstock, resulting in the inability to comprehensively utilize low-grade sulfide ore resources. Furthermore, traditional heap leaching technology only treats oxide ores and has not been applied to the heap leaching treatment of encapsulated sulfide ores, especially low-grade sulfide ore resources.

[0003] After long-term research, technical personnel proposed optimizing the entire heap leaching process from three aspects: ore property analysis, ore pretreatment, and crushing, to solve existing problems. Specifically, ore pretreatment needs to consider desulfurization, iron removal, and arsenic removal to reduce the adverse effects on the leaching process. The crushing process considers ore particle size control and improving the permeability of the sodium cyanide solution during spraying, ensuring sufficient contact and reaction between the ore and the solution, and increasing the gold leaching rate. This invention aims to overcome the difficulties in the heap leaching utilization of low-grade sulfide mineral resources and promote its widespread application. Summary of the Invention

[0004] This invention provides a method for heap leaching gold extraction from low-grade sulfide gold ore.

[0005] The specific technical solution of the present invention is as follows: a seepage-proof base is laid at the heap leaching site; quicklime is used to pretreat the sulfide gold ore; the ore is crushed; the ore is transported to the top of the base and piled up; pipes are installed on the top and slopes of the ore pile to spray and collect the gold-bearing precious solution, the spray solution being a sodium cyanide solution; and activated carbon is used to adsorb and recover gold from the gold-bearing precious solution.

[0006] Furthermore, preferably, an impermeable mat is laid by overlapping and cross-laying 8m×30m composite plastic woven fabric and 8m×50m polyethylene film.

[0007] Furthermore, preferably, the sulfide gold ore is transported to the stockpile, and during the stockpiling process, a loader is used to initially add quicklime, and then an excavator is used to mix the ore and lime evenly. After stockpiling for 3 to 5 days, the ore changes from smoky gray to reddish brown, completing the removal of iron, sulfur, and arsenic.

[0008] By adding quicklime (calcium oxide) to sulfide ores for mixing, the alkalinity, exothermic properties, and chemical reactivity of quicklime are utilized to selectively inhibit and transform pyrite (FeS2), sulfides, and arsenic minerals. The specific mechanism is as follows: (1) Inhibition of pyrite and removal of iron: quicklime reacts with water to produce calcium hydroxide (Ca(OH)2), releasing a large amount of heat and providing OH. - Ions. In an alkaline environment, an oxidation-precipitation reaction occurs on the surface of pyrite, generating ferrous hydroxide (Fe(OH)2) and ferric hydroxide (Fe(OH)3), forming a dense and stable surface passivation film. This effectively blocks the contact between pyrite and the subsequent cyanidation solution, inhibiting the oxidative cyanide consumption behavior. Furthermore, the Ca in the solution... 2+ The ions can combine with SO4²⁻ released from the oxidation of pyrite to form insoluble calcium sulfate (CaSO4) precipitate, which further coats the mineral surface and enhances the inhibition effect. This dual mechanism significantly reduces iron dissolution and cyanide consumption.

[0009] (2) Sulfide desulfurization mechanism: Sulfide minerals (such as pyrite, pyrrhotite, etc.) are partially oxidized to sulfur dioxide (SO2) or sulfate (SO4) under the exothermic hydration of quicklime (CaO) and alkaline conditions. 2- First, SO2 is absorbed by Ca(OH)2 to form calcium sulfite (CaSO3); then, calcium sulfite is oxidized by oxygen in the air to form stable calcium sulfate (CaSO4). Calcium sulfate has low solubility and high thermal stability, and is not easily decomposed or dissolved, thus permanently fixing sulfur in solid form in the ore heap, reducing the risk of sulfur leaching and acidification during subsequent heap leaching.

[0010] SO2 + Ca(OH)2 → CaSO3 + H2O 2CaSO3 + O2 → 2CaSO4 (3) Arsenic removal and co-precipitation mechanism: Arsenic in sulfide ores mainly exists in the form of arsenopyrite (FeAsS) or arsenic pyrite, which can be oxidized to arsenite (AsO3³) under alkaline oxidation conditions. - ) or arsenate (AsO4³ - The Ca(OH)₂ generated from the hydration of quicklime can react with these arsenic-containing anions to form insoluble calcium arsenate or calcium arsenite precipitates. Simultaneously, under oxidizing conditions, Fe… 2+ Oxidized to Fe 3+ It then hydrolyzes to generate ferric hydroxide colloid (Fe(OH)3). This colloid has a huge specific surface area and strong adsorption capacity. It can encapsulate and precipitate Ca3(AsO3)2, Ca3(AsO4)2 and fine suspended impurities through an adsorption-coprecipitation mechanism, thereby achieving efficient fixation and separation of arsenic.

[0011] 3Ca2+ + 2AsO4³ - → Ca3(AsO4)2↓ 3Ca 2+ + 2AsO3³ - → Ca3(AsO3)2↓ Fe 3+ + 3OH - → Fe(OH)3 (colloid) This is fundamentally different from "continuously adding quicklime (Ca(OH)2) or sodium hydroxide (NaOH) during conventional heap leaching to adjust pH and inhibit CN⁻ hydrolysis and volatilization".

[0012] Furthermore, preferably, the consumption of quicklime is 25-30 kg / t.

[0013] Furthermore, preferably, the pretreated ore is crushed using a two-stage closed-circuit process, with a jaw crusher (PE900×1200) for primary crushing and a cone crusher (HPM400) for medium and fine crushing, with a crushing particle size ≤2cm.

[0014] Since over 60% of low-grade gold sulfides exist as micro / submicroscopic inclusions within pyrite, arsenopyrite lattices, or quartz fractures, two-stage closed-circuit crushing can liberate 95% of the sulfide ore aggregates, exposing the gold surface. Simultaneously, this crushing particle size comprehensively considers the "economically viable leaching threshold," ensuring leaching efficiency and profitability.

[0015] Furthermore, preferably, the crushed ore is transported to the bottom of the stockpile using ore trucks and piled up to a height of less than 5m. After the pile is built, an excavator is used to turn over the loose ore pile.

[0016] Furthermore, preferably, a sodium cyanide solution is sprayed onto the top of the ore pile and the slope to collect the gold-bearing liquid.

[0017] Furthermore, preferably, the gold-containing precious liquid is introduced into the adsorption workshop through pipelines and the gold is enriched using an adsorption tower filled with activated carbon.

[0018] The beneficial effects of this invention are as follows: This invention can efficiently remove harmful impurities such as iron, sulfur, and arsenic through quicklime pretreatment, cutting off the main cause of cyanide consumption at the source. Furthermore, the invention utilizes fine crushing at ≤2cm to fully dissociate gold-bearing sulfides, significantly improving the selectivity of gold leaching and the stability of the solution. Simultaneously, it reduces cyanide consumption, leaching cycle, and leaching cost, achieving an overall transformation from "high cyanide consumption, high pollution, and high cost" to "heap leaching, low reagent consumption, and high profitability." The process is simple, the equipment is conventional, and it is economical and environmentally friendly. It can be replicated and promoted to similar low-grade sulfide gold mines. Attached Figure Description

[0019] Figure 1 This is the original heap leaching process flow chart; Figure 2 This is a flow chart of the heap leaching process for sulfide ores. Detailed Implementation

[0020] To make the technical problems and solutions solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0021] In the description of this invention, it should be understood that the terms "oxidized ore", "sulfide ore", "seepage-proof bottom pad", "crushing", "particle size", "heaping", "leaching", "adsorption", etc. are professional terms used in geology and mineral processing (heap leaching) technology, and therefore should not be construed as limiting this description.

[0022] like Figure 2 As shown, a method for extracting gold from low-grade sulfide gold ore through heap leaching includes laying an impermeable base at the heap leaching site; pretreatment of the sulfide gold ore; ore crushing; ore being transported and piled on top of the base; spraying gold-bearing precious solution through pipes on the top and slopes of the ore pile, the spraying solution being a sodium cyanide solution; and gold being recovered by adsorption of the gold-bearing precious solution using activated carbon.

[0023] Depend on Figures 1 to 2 A comparison reveals that the heap leaching method for extracting gold from low-grade sulfide gold ore proposed in this application involves the following modifications to the existing heap leaching process: 1. To mitigate the adverse effects of elements such as iron, sulfur, and arsenic in sulfide ores on the leaching process, quicklime is added before heap leaching. This pre-treatment removes impurities, reducing cyanide consumption and minimizing the impact of iron / sulfur / arsenic, thereby improving gold leaching selectivity and solution stability. This differs from conventional heap leaching methods that continuously add hydrated lime (Ca(OH)2) or sodium hydroxide (NaOH) to adjust pH and inhibit CN2. - The process control of "hydrolysis and volatilization" is fundamentally different.

[0024] 2. To ensure thorough mixing of sulfide ore and quicklime, an excavator was used to mix the ore and quicklime. The sulfide ore was transported to the crushing station's stockpile. During the transport, quicklime was added to the stockpile according to the lime consumption of a small-scale test. After stockpiling for 3-5 days, the sulfide ore and quicklime were evenly mixed using an excavator.

[0025] 3. In order to fully dissociate the sulfide ore aggregates, fully expose the gold surface, and ensure the contact area between gold and sodium cyanide solution, the ore crushing process was increased. At the same time, to ensure the permeability of the solution in the ore pile during leaching, the pre-treated ore was crushed to ≤2cm and then transported to the stockpile for heaping. Application Example 1

[0026] A low-gold heap leaching mine: A heap leaching + activated carbon adsorption process was adopted, applying the heap leaching gold extraction method for low-grade sulfide gold ore described in this application. A semi-industrial production test of heap leaching was conducted on this type of sulfide gold ore. The specific implementation plan is as follows: 1. Properties of gold sulfide ore: Smoky gray, grayish-green, dark green; diabase, gabbroic texture, massive structure, fine-grained disseminated structure, locally brecciated structure, and a small amount of veinlet structure. The ore-bearing rock is mainly altered diabase. The ore mineral composition is pyrite, stibnite, and a small amount of arsenopyrite and arsenopyrite. Gangue mineral composition is pyroxene, basic plagioclase, quartz, etc. The ore mineral composition is pyrite in veins and fine-grained disseminated forms, stibnite, a small amount of arsenopyrite, arsenopyrite, and locally oxidized pyrite in fissures forming fine veins, disseminated goethite (hematite). The ore belongs to colloidal pyrite formed by medium-low temperature hydrothermal activity, often associated with arsenopyrite. Stibnite occurs as lenticular, nodular, and disseminated veins, with a euhedral to semi-euhedral texture, a few as fine-grained disseminated forms, and most as thin-film disseminated forms due to oxidation. Arsene is sparsely disseminated as euhedral granules, with a grain size generally ranging from 0.1 to 0.3 mm, and often occurs in association with pyrite. Gold is found primarily as isomorphous sulfides such as arsenopyrite, pyrite, and stibnite. It also occurs partially as a native element in native gold, native silver, silver-gold ores, and gold-silver ores, exhibiting very low abundance in native silver and higher abundance in native gold.

[0027] 2. Main process of heap leaching (1) Transport the sulfide ore to the crushing station stockpile. During the transport process, add lime (quicklime) to the stockpile according to the previous small-scale test of 25 kg / t. Use an excavator to mix the sulfide ore and quicklime evenly and stockpile for a reaction period of 2 to 3 days.

[0028] (2) Use a loader to pour the stockpiled sulfide ore into the crushing process for crushing, and crush the particle size ≤2cm. Continue to stockpile the crushed ore for 2 to 3 days. After the sulfide ore turns brownish-red or light yellow, it can be transported to the stockpile with a seepage-proof bottom pad for stockpiling.

[0029] (3) During the pile building process, the pH value of the ore is sampled and tested daily to see if it is ≥10 (observe the pH of the hydrolysis solution of the ore). If it does not meet the requirements, add an appropriate amount of quicklime during the pile building process; after the transfer is completed, use an excavator to turn the entire pile over (loose ore).

[0030] (4) Spray pipes are installed on the top and sides of the ore pile, and sodium cyanide solution is prepared at a concentration of 1‰ for spraying. The gold-containing precious solution is introduced into the mineral processing adsorption workshop through the pipes to adsorb and recover gold.

[0031] The semi-industrial production test ore volume was 13467.14t, the raw ore grade was 1.102g / t, and the raw ore metal content was 14.839kg. Spraying treatment started on August 5, 2021, and ended on December 4, 2021.

[0032] After the above heap leaching process, the technical and economic indicators are as follows: tailings grade 0.39 g / t, tailings liquid grade 0.1 mg / L, leaching rate 64.61%, comprehensive recovery rate 62.11%, and gold production 9.218 kg. The total input cost of this experimental heap was 968,100 yuan, the average cost per ton of ore was 71.89 yuan / t, and the economic benefits generated were ≥2 million yuan. Application Example 2

[0033] A certain low-grade gold heap leaching (low-grade + cyanide tailings) mine No. 2: Heap leaching + activated carbon adsorption process is used to treat low-grade waste tailings ore. In 2023, the sulfide gold ore in the waste tailings mine will be centrally processed using the heap leaching gold extraction method for low-grade sulfide gold ore described in this application. The specific implementation plan is as follows: (1) Transport the sulfide ore to the crushing station stockpile. During the transport process, add lime (quicklime) to the stockpile according to the previous small-scale test of 30 kg / t. Use an excavator to mix the sulfide ore and quicklime evenly and stockpile for a reaction period of 2 to 3 days.

[0034] (2) Use a loader to pour the stockpiled sulfide ore into the crushing process for crushing, and crush the particle size ≤2cm. Continue to stockpile the crushed ore for 2 to 3 days. After the sulfide ore turns brownish-red or light yellow, it can be transported to the stockpile with a seepage-proof bottom pad for stockpiling.

[0035] (3) During the pile building process, the pH value of the ore is sampled and tested daily to see if it is ≥10 (observe the pH of the hydrolysis solution of the ore). If it does not meet the requirements, add an appropriate amount of quicklime during the pile building process; after the transfer is completed, use an excavator to turn the entire pile over (loose ore).

[0036] (4) Spray pipes are installed on the top and sides of the ore pile, and sodium cyanide solution is prepared at a concentration of 1‰ for spraying. The gold-containing precious solution is introduced into the mineral processing adsorption workshop through the pipes to adsorb and recover gold.

[0037] After the above heap leaching process, the technical and economic indicators are as follows: raw ore grade 0.81 g / t, tailings grade 0.41 g / t, tailings liquid grade 0.1 mg / L, leaching rate 50.08%, comprehensive recovery rate 46.35%, 61,100 tons of sulfide gold ore were processed, producing 23.07 kg of gold, generating economic benefits of approximately 6 million yuan.

[0038] As can be seen from the technical and economic indicators of the above application examples, the heap leaching method for extracting gold from low-grade sulfide gold ore described in this application can be applied to heap leaching to process sulfide gold ore, and the technical and economic indicators are good, and the mineral resources are fully developed and utilized.

[0039] The present invention has been described in detail above through specific and preferred embodiments. However, those skilled in the art should understand that the present invention is not limited to the embodiments described above. Any modifications or equivalent substitutions made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for gold extraction from low-grade sulphidic gold ores by heap leaching, comprising a plurality of mutually connected operations, characterized in that: Laying impermeable base pad in heap leaching site; using quicklime for pre-treatment of sulfide gold ore; ore crushing operation; heap building operation; spraying operation; carbon adsorption operation.

2. A method for heap leaching gold from a low-grade sulphidic gold ore according to claim 1, characterized in that: 8m×30m composite plastic woven cloth and 8m×50m polyethylene film are overlapped and cross-laid to form impermeable ground pad.

3. A method for heap leaching gold from a low-grade sulphidic gold ore according to claim 2, characterized in that: The sulfide gold ore is transported to the ore stacking site, and quicklime is added by loader during stacking, then the ore and lime are mixed evenly by excavator, and the ore is stacked for 3-5 days, during which the ore color changes from ash to red-brown, and the iron removal, desulfurization and arsenic removal are completed.

4. A method for heap leaching gold from a low-grade sulphidic gold ore according to claim 3, characterized in that: The consumption of quicklime is 25-30kg / t.

5. A method for heap leaching gold from a low-grade sulphidic gold ore according to claim 3, characterized in that: The pre-treated ore is crushed by two-stage closed circuit process, the primary crushing is carried out by jaw crusher, and the medium and fine crushing is carried out by cone crusher, and the crushing size is ≤2cm.

6. A method for the heap leaching of gold from a low grade sulphidic gold ore according to claim 5, characterised in that: The crushed ore is transported to the base pad of the heap site by ore car, and the heap height is <5m, and the heap is loosened by excavator after the heap building is completed.

7. A method for the heap leaching of gold from a low grade sulphidic gold ore according to claim 6, characterised in that: The pipes are erected on the top and slope of the heap, and sodium cyanide solution is sprayed, and the gold-containing pregnant solution is collected.

8. A method for heap leaching gold from a low-grade sulphidic gold ore according to claim 7, characterized in that: The gold-containing pregnant solution is introduced into the adsorption workshop by pipeline, and the activated carbon adsorption tower is used for gold enrichment.

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