A low-grade gold-bearing medium enrichment, roasting and leaching process

Abstract

The application provides a low-grade wrapped gold heavy medium enrichment, roasting and leaching process, and belongs to the field of mineral resources processing. The process comprises the following steps: S1, in a continuous suspension roasting system, under the conditions of a roasting temperature of 480-520 DEG C and an oxygen concentration of 8-12%, fine particle wrapped gold ore is subjected to suspension roasting to obtain roasted concentrate; S2, the roasted concentrate is subjected to two-stage ball milling to obtain ball mill slurry; S3, under the conditions of a ball mill slurry concentration of 40-50%, a temperature of 20-30 DEG C and a pH of 10.5-11.5, the ball mill slurry is subjected to leaching treatment by using a composite gold leaching agent to obtain leaching slurry. By constructing a whole-process collaborative system of "roasting pretreatment-milling connection-leaching adaptation", the process barriers between roasting and leaching are broken, a continuous optimal recovery environment is created for various types of fine particle wrapped gold, and the leaching rate, stability and economy of wrapped gold are simultaneously improved.

Description

Technical Field

[0001] This application relates to the field of mineral resource processing technology, and in particular to a process for enriching, roasting and leaching low-grade gold-encapsulated heavy media. Background Technology

[0002] Fine-grained gold inclusions are an important gold resource in my country, but their efficient recovery has always been a major technical challenge in the beneficiation and metallurgical field. Currently, industrial processing technologies for this type of ore mainly include direct cyanide leaching, conventional roasting-leaching, and bioleaching. While direct cyanide leaching is simple, it lacks pretreatment of the gold inclusions, and the fine-grained inclusions severely hinder the contact between the leaching agent and the gold, resulting in a gold leaching rate of only 60-70%, leading to significant resource waste. Conventional roasting-leaching decomposes fine-grained inclusions through thermal pretreatment, but its roasting temperature is often in the high-temperature range of 600-700℃, which easily leads to ore sintering and secondary gold encapsulation, further hindering gold exposure and resulting in limited leaching rate improvement (75-80%), and also suffers from excessive energy consumption. Although bioleaching is environmentally friendly, its reaction cycle is long (7-10 days), and it is extremely sensitive to environmental factors such as temperature and pH, exhibiting poor process stability and failing to meet the efficiency and stability requirements for large-scale industrial applications.

[0003] The root cause lies in the systemic flaws of existing processes: treating roasting and leaching as independent steps, failing to integrate and coordinate the design of key roasting parameters (temperature, atmosphere) and subsequent leaching parameters (grinding fineness, reagent formulation) to address the characteristics of finely encapsulated gold. This disconnect in the process chain prevents upstream output from creating optimal conditions for downstream processes, leading to a series of problems such as low leaching rates, insufficient process stability (leaching rate fluctuation ≥5%), high overall costs, and poor adaptability to different ores. Therefore, existing technologies cannot create a continuous, stable, and efficient optimal recovery environment for finely encapsulated gold. The fundamental technical problem lies in the severe disconnect between the two key processes of roasting and leaching, and the isolation of system process parameters, which severely restricts the simultaneous improvement of leaching rates, stability, and economic efficiency. This application aims to address this systemic technical bottleneck. Summary of the Invention

[0004] This application provides a process for enriching, roasting, and leaching low-grade gold-encapsulated particles in heavy media to solve the following technical problems: In the prior art, the two key processes of roasting and leaching are disconnected from each other, which cannot create a continuously optimal recovery environment for various types of fine-particle gold encapsulation, thus restricting the simultaneous improvement of leaching rate, stability, and economy.

[0005] This application provides a process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media, the process comprising the following steps:

[0006] S1. In a continuous suspension roasting system, fine-grained gold concentrate is suspended roasted at a roasting temperature of 480–520℃ and an oxygen concentration of 8–12% to obtain roasted concentrate.

[0007] S2. The roasted concentrate is subjected to two-stage ball milling to obtain ball mill slurry;

[0008] S3. Under the conditions of ball mill slurry concentration of 40-50%, temperature of 20-30℃ and pH of 10.5-11.5, the ball mill slurry is leached using a composite gold leaching agent to obtain leached slurry.

[0009] The composite gold immersion agent, by mass, is composed of the following chemical components: 45-65 parts ammonium thiosulfate, 8-15 parts urea, 1-4 parts copper sulfate, 0.05-0.5 parts sodium dodecyl sulfonate, and 5-15 parts citric acid.

[0010] Optionally, the grade of the fine-grained gold concentrate is 0.96–1.0 g / t.

[0011] Optionally, the fine-grained gold concentrate is a mixture of heavy media pre-enriched concentrate and heavy media separation tailings from the same ore, which have been ground to -0.5 mm. The grade of the heavy media pre-enriched concentrate is 1.04 to 1.08 g / t, and the heavy media separation tailings are low-density products obtained after heavy media separation.

[0012] Optionally, the continuous suspension roasting system includes a feeding hopper, a loss-in-weight scale, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system, and the roasting atmosphere is maintained by controlling the loosening air and fluidizing air introduced into the suspension roasting furnace.

[0013] Optionally, the nitrogen flow rate of the loosening air is 2.0–2.2 m³ / h. 3 / h, airflow rate is 1.8~2.0m 3 The nitrogen flow rate of the fluidizing air is 3.6–3.8 m³ / h. 3 / h, airflow rate is 3.2~3.4m 3 / h.

[0014] Optionally, the feed rate for suspension roasting is 18–22 kg / h.

[0015] Optionally, the grade of the roasted concentrate is 1.11-1.15 g / t, the loss on ignition is ≤10%, and the decomposition rate of the fine-grained gold concentrate is ≥90%.

[0016] Optionally, the two-stage ball milling includes:

[0017] First, the roasted concentrate is ball-milled until the proportion of material with a particle size of less than 200 mesh is ≥90%.

[0018] The material after the first ball milling is then subjected to a second ball milling process until the proportion of material with a particle size of less than 400 mesh is ≥95%.

[0019] Optionally, the amount of the composite gold leaching agent is 55-65 kg / t dry ore;

[0020] The leaching treatment is performed at a temperature of 20–30°C for 20–28 hours.

[0021] Optionally, the process further includes the following steps:

[0022] S4. The leaching slurry is subjected to solid-liquid separation to obtain precious solution and leaching residue;

[0023] The grade of the precious liquor is 4.0-4.5 g / t, and the grade of the leaching residue is 0.15-0.17 g / t.

[0024] The technical solutions provided in this application have the following advantages compared with the prior art:

[0025] This application provides a process for enriching, roasting, and leaching low-grade gold-encapsulated gold in heavy media. By constructing a collaborative system of "roasting pretreatment - grinding connection - leaching adaptation", it breaks down the process barriers between roasting and leaching, creating a continuously optimal recovery environment for fine-particle gold encapsulation and fundamentally solving the problem of their disconnect.

[0026] First, the roasting process (S1) is not carried out in isolation, but is precisely controlled according to the leaching requirements: the continuous suspension roasting system transforms the fine-grained gold concentrate into a porous roasted concentrate at a mild temperature of 480-520℃ and an oxygen concentration of 8-12%. This not only completely destroys the fine-grained structure and exposes the fine gold particles, but also avoids ineffective sintering or secondary encapsulation, creating a "reactive" material basis for subsequent leaching and achieving pre-adaptation of roasting to leaching.

[0027] Secondly, the second-stage ball milling process (S2) is a key connecting link. It performs graded dissociation based on the porous characteristics of the roasted concentrate, so that the gold particles can be fully freed from the carrier and form a free surface that can be efficiently contacted with the leaching agent. This builds a "material bridge" between the roasting product and the leaching reaction, avoiding the disconnect between the roasting effect and the degree of particle dissociation.

[0028] Finally, the parameter design and reagent formulation of the leaching process (S3) fully inherit the results of the front-end process: 40-50% slurry concentration, 20-30℃ temperature and 10.5-11.5 pH value, which are precisely adapted to the characteristics of the porous dissociated material to ensure a stable reaction environment; the composite gold leaching agent is designed for the extraction of fine gold particles. Through the complexing effect of ammonium thiosulfate, the catalytic effect of copper sulfate and the stabilizing effect of urea, the multi-component synergy can efficiently capture the dissociated gold particles, and achieve precise acceptance of the roasting-grinding products by leaching.

[0029] Thus, in the entire process, roasting provides an "easy-to-leach structure" for leaching, grinding provides "accessible particles" for leaching, and leaching provides an "efficient conversion environment" for the front-end results. Each process is interconnected and complementary, forming a continuously adaptable recycling chain. This completely changes the situation in the existing technology where the two processes are independent and the parameters are disconnected, thereby achieving a simultaneous improvement in leaching rate, stability, and economy. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic flowchart illustrating a process for enriching, roasting, and leaching a low-grade encapsulated gold heavy medium, as provided in an embodiment of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0035] Figure 1 This is a schematic flowchart illustrating a process for enriching, roasting, and leaching a low-grade encapsulated gold heavy medium, as provided in an embodiment of this application.

[0036] like Figure 1 As shown, this application provides a process for enriching, calcining, and leaching low-grade gold-encapsulated heavy media, the process comprising the following steps:

[0037] S1. In a continuous suspension roasting system, fine-grained gold concentrate is suspended roasted at a roasting temperature of 480–520℃ and an oxygen concentration of 8–12% to obtain roasted concentrate.

[0038] S2. The roasted concentrate is subjected to two-stage ball milling to obtain ball mill slurry;

[0039] S3. Under the conditions of ball mill slurry concentration of 40-50%, temperature of 20-30℃ and pH of 10.5-11.5, the ball mill slurry is leached using a composite gold leaching agent to obtain leached slurry.

[0040] The composite gold immersion agent, by mass, is composed of the following chemical components: 45-65 parts ammonium thiosulfate, 8-15 parts urea, 1-4 parts copper sulfate, 0.05-0.5 parts sodium dodecyl sulfonate, and 5-15 parts citric acid.

[0041] In some embodiments, the process further includes the following steps:

[0042] S4. The leaching slurry is subjected to solid-liquid separation to obtain precious solution and leaching residue;

[0043] The grade of the precious liquor is 4.0-4.5 g / t, and the grade of the leaching residue is 0.15-0.17 g / t.

[0044] It should be noted that the suspension roasting step (S1) is the core of the entire pretreatment process, and its key function is to break down the gold encapsulation structure of fine particles. Through the dynamic reaction environment of the continuous suspension roasting system, the gold concentrate with fine particles undergoes oxidative transformation in a specific atmosphere, decomposing the originally dense fine particle carrier into a porous and loose oxide structure. This initially exposes the encapsulated fine gold particles, creating a structural basis for subsequent grinding and leaching steps, while simultaneously achieving initial gold enrichment and improving the gold grade of the roasted concentrate.

[0045] The core function of the two-stage ball milling step (S2) is to achieve full dissociation of gold particles. Based on the porous and loose characteristics of the roasted concentrate, the particle size of the material is gradually optimized through staged grinding: the first-stage ball milling completes the initial crushing and dissociation of the material, enabling most of the material to reach the basic dissociation particle size; the second-stage ball milling further refines the particle size, ensuring that the gold particles are completely freed from the binding of the oxide carrier, forming a free surface that can fully contact the composite gold leaching agent, providing the material contact prerequisite for the leaching reaction, while avoiding energy waste caused by over-grinding.

[0046] The leaching process (S3) is a crucial step in gold recovery. Its core function is to dissolve and transfer gold through the chemical interaction between the composite leaching agent and gold particles. In a precisely controlled slurry environment, the functional components of the composite leaching agent work synergistically to oxidize and complex the fully dissociated gold particles, transforming the solid gold into water-soluble gold complexes. This allows the gold to be transferred from the ball-milled slurry into the liquid phase, completing the chemical extraction process.

[0047] The core function of the solid-liquid separation step (S4) is to achieve the physical separation and enrichment of gold. Through the separation operation, the liquid phase and solid phase in the leaching slurry are completely separated, resulting in a precious solution rich in gold complexes and the remaining leaching residue after gold extraction. This concentrates the gold in the form of soluble complexes, providing high-grade raw materials for the final recovery of gold. At the same time, it completes the preparation for the harmless treatment of the leaching residue, achieving effective separation of resources and waste.

[0048] Meanwhile, the functions of each component in the composite gold immersion agent are as follows:

[0049] Ammonium thiosulfate (45–65 parts) serves as the main complexing agent and is the core functional component of the gold leaching system. The thiosulfate ion in its molecular structure possesses strong complexing ability, rapidly combining with monovalent gold ions generated through oxidation to form a stable water-soluble complex [Au(S₂O₃)₂]. 3- The transfer of gold from the surface of solid particles into solution is the core material basis for achieving gold dissolution and recovery.

[0050] Citric acid (5-15 parts) serves a dual function of interface modification and catalytic assistance. Multiple carboxyl groups in its molecule can undergo complexation reactions with trace impurities on the surface of the calcined product, gently dissolving and removing adhering impurities from the gold particle surface, thus cleaning the gold surface and clearing the contact channels between the composite gold immersion agent and the gold particles. Simultaneously, citric acid can form stable complexes with copper ions, optimizing the catalytic activity and improving the oxidation reaction efficiency.

[0051] Copper sulfate (1–4 parts) acts as a catalytic oxidant and is the kinetically driving component of the leaching reaction. The copper ions it provides form Cu. 2+ / Cu + Redox couples can efficiently transfer electrons, oxidizing elemental gold to monovalent gold ions. After being reduced to low-valent copper ions, they can be rapidly regenerated into high-valent copper ions by dissolved oxygen in the solution, achieving a catalytic cycle and continuously accelerating the oxidation and dissolution rate of gold.

[0052] Urea (8-15 parts) acts as a system stabilizer, providing a long-term stable environment for the leaching reaction. The amide groups in its molecule form a dynamic stable network with thiosulfate ions, water molecules, and citric acid molecules through hydrogen bonding, effectively inhibiting the hydrolysis and decomposition of ammonium thiosulfate under alkaline conditions. Simultaneously, it stabilizes intermediates in the catalytic reaction process, ensuring the leaching system maintains stable chemical activity during long-term reactions and preventing the deactivation of effective components.

[0053] Sodium dodecyl sulfonate (0.05–0.5 parts), as a surface-active penetrant, is a key component for enhancing the leaching range of the reagent. Its amphiphilic molecular structure can significantly reduce the surface tension of the leaching solution, enhance the wetting ability of the solution on the porous structure of the roasted concentrate, and guide the effective components of the composite gold leaching agent to quickly penetrate into the depths of the nanoscale pores of the material, ensuring that all exposed fine gold particles can fully contact the reagent and avoiding leaching dead zones caused by insufficient penetration.

[0054] More importantly, the components of the composite leaching agent form a continuous reaction chain of "penetration-cleaning-catalysis-oxidation-complexation-stabilization" through functional coupling, achieving a synergistic improvement in leaching efficiency. First, sodium dodecyl sulfate acts as a penetrant, reducing the surface tension of the solution, allowing the composite leaching agent to quickly wet the material surface and penetrate into the pores. Subsequently, citric acid removes impurities and modifies the interface on the surface of the gold particles and the inner walls of the pores, clearing obstacles for subsequent reactions, while simultaneously forming a synergistic catalytic system with copper ions provided by copper sulfate. Then, Cu... 2+ / Cu + The efficient oxidation of elemental gold by the electrochemical couple results in monovalent gold ions. Ammonium thiosulfate immediately complexes with these monovalent gold ions to form a water-soluble complex, completing the dissolution and transfer of gold. Throughout the reaction, urea stabilizes ammonium thiosulfate and the catalytic intermediate through a hydrogen bond network, preventing the decomposition and inactivation of the effective components and ensuring the continuous and efficient progress of the reaction chain. This synergistic effect allows the functions of each component to complement and reinforce each other, leveraging the core functions of individual components while enhancing the overall performance of the leaching system through a coupling effect. This creates a dual physical and chemical compatibility with the porous structure of the roasted concentrate, achieving highly efficient gold leaching.

[0055] In some embodiments, the grade of the fine-grained encapsulated gold concentrate is 0.96–1.0 g / t.

[0056] The limited grade of fine-grained gold concentrate (0.96–1.0 g / t) provides a basis for the material characteristics of the process design, ensuring the matching of subsequent roasting, grinding and leaching parameters, and guaranteeing that the process can stably achieve enrichment and leaching effects within this raw material grade range.

[0057] In some embodiments, the fine-grained gold concentrate is a mixture of heavy media pre-enriched concentrate and heavy media separation tailings from the same ore that have been ground to -0.5 mm. The grade of the heavy media pre-enriched concentrate is 1.04 to 1.08 g / t, and the heavy media separation tailings are low-density products obtained after heavy media separation.

[0058] It should be noted that the "fine-grained gold concentrate" described in this application is a targeted raw material system designed for the efficient recovery of low-grade gold ore resources. Its core feature is a synergistic mixing system of two sorting products from the same raw ore source, which aims to maximize the utilization of mineral resources and ensure the adaptability of subsequent processes.

[0059] Among them, "fine-grained gold concentrate" refers to mineral raw materials in which gold elements are mainly stored in the form of fine grains inside or in the interstitial spaces of fine-grained crystals (such as pyrite, chalcopyrite, etc.), and are encapsulated by a dense fine-grained structure. It requires specific pretreatment to destroy the fine-grained encapsulation layer in order to achieve efficient gold leaching, which is different from conventional gold concentrates in which gold particles are directly exposed or simply embedded.

[0060] "Heavy media pre-enriched concentrate" is a core component with relatively high gold content obtained after the raw ore is processed by heavy media separation process (a separation technology that uses the density difference between heavy media and minerals to separate minerals). Its gold content is controlled at 1.04 to 1.08 g / t. This component retains most of the fine-grained gold with recovery value in the raw ore and is the main contributor to gold in the mixed raw materials.

[0061] "Heavy media separation tailings" are separation byproducts from the same source as the pre-enriched concentrate. They refer to mineral components with relatively low gold grade after heavy media separation, but still containing a certain amount of recoverable fine-grained gold-encapsulated mineral components. After being ground to -0.5mm (i.e., all material particles are less than 0.5 mm), they are mixed. On the one hand, the grinding action initially breaks down some of the coarse-grained fine-grained structures. On the other hand, it ensures that the particle size is compatible with the heavy media pre-enriched concentrate, avoiding excessive particle size differences after mixing that could affect the uniformity of the subsequent roasting process.

[0062] "Same raw ore" is a key prerequisite for the raw material system. It emphasizes that the two components originate from the same mineral resource, which can ensure that the type of fine particles, the gold inclusion morphology and mineral composition characteristics in the mixed raw materials are highly consistent. This avoids the process parameter adaptation conflicts caused by different raw ores from the source and provides a foundation for the stable operation of subsequent roasting and leaching processes.

[0063] "Grade" specifically refers to the mass of gold contained in a unit mass of mineral raw material. In this application, the grade of the heavy media pre-enriched concentrate is 1.04–1.08 g / t, meaning that each ton of this concentrate contains 1.04–1.08 grams of gold. This directly reflects its enrichment effect and provides a core reference for the overall grade control of the mixed raw materials and the subsequent optimization of reagent dosage and process parameters. The mixed design of the above two components not only realizes the secondary utilization of the remaining recoverable gold in the heavy media separation tailings, but also ensures the homogeneity of the raw material system through particle size adaptation and component homology, laying a key material foundation for the uniform reaction of subsequent continuous suspension roasting and the full decapsulation of gold.

[0064] By limiting the grade of the heavy media pre-enriched concentrate (1.04–1.08 g / t) and the grinding particle size of the heavy media separation tailings (-0.5 mm), the initial material composition and particle size distribution of the raw materials are optimized by mixing the pre-enriched concentrate of a specific grade with the separation tailings of a limited particle size, thus providing a high-quality raw material basis for uniform oxidation and efficient enrichment in suspension roasting.

[0065] In some embodiments, the continuous suspension roasting system includes a feed hopper, a loss-in-weight scale, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system, and the roasting atmosphere is maintained by controlling the loosening air and fluidizing air introduced into the suspension roasting furnace.

[0066] The continuous suspension roasting system consists of (feeding bin, loss-in-weight scale, suspension roasting furnace, cyclone separator, vertical cooler, and dust collection system): each component works together to achieve continuous feeding of raw materials, precise temperature control, uniform roasting, rapid cooling, and exhaust gas treatment, ensuring the continuity, stability, and environmental friendliness of the roasting process, and providing a controllable process environment for the oxidation reaction.

[0067] In some embodiments, the nitrogen flow rate of the loosening air is 2.0–2.2 m³ / h. 3 / h, airflow rate is 1.8~2.0m 3 The nitrogen flow rate of the fluidizing air is 3.6–3.8 m³ / h. 3 / h, airflow rate is 3.2~3.4m 3 / h.

[0068] A limited roasting temperature (480–520°C) provides suitable thermodynamic conditions for the oxidative decomposition of fine particles, ensuring that the fine particles are fully decomposed while generating porous hematite, creating a structural advantage for gold exposure and subsequent leaching.

[0069] By limiting the oxygen concentration (8-12%), a mild oxidizing atmosphere is created, which can meet the needs of fine particle oxidative decomposition while avoiding material sintering or secondary encapsulation caused by excessive oxidation, thus ensuring the porous and loose characteristics of the roasted concentrate.

[0070] Limit the loosening air parameters (nitrogen flow rate 2.0~2.2m). 3 / h, air flow rate 1.8~2.0m 3 / h) and fluidizing air parameters (nitrogen flow rate 3.6~3.8m) 3 / h, airflow rate 3.2~3.4m 3 By precisely controlling the flow ratio of the two gases ( / h), a stable fluidization state is maintained in the suspension roasting furnace, ensuring full contact between the material and the gas. At the same time, the oxygen concentration in the furnace is precisely controlled to ensure the consistency of the roasting atmosphere.

[0071] In some embodiments, the feed rate for suspension roasting is 18–22 kg / h.

[0072] The feed rate for suspension roasting is limited (18-22 kg / h), and the feed rate is matched with the volume and gas flow rate of the suspension roasting furnace to ensure that the material has sufficient reaction residence time in the furnace, so that the fine particles are completely oxidized and decomposed, thereby improving the grade and quality of the roasted concentrate.

[0073] In some embodiments, the grade of the roasted concentrate is 1.11 to 1.15 g / t, the yield is ≥40%, and the loss on ignition is ≤10%.

[0074] The performance indicators of roasted concentrate (grade 1.11~1.15g / t, yield ≥40%, decomposition rate of fine-grained gold concentrate ≥90%) are a direct reflection of the roasting effect, ensuring that the roasting step achieves effective enrichment of gold, while controlling material loss within a reasonable range, so as to provide high-quality raw materials for subsequent grinding and leaching steps.

[0075] In some embodiments, the two-stage ball milling includes:

[0076] First, the roasted concentrate is ball-milled until the proportion of material with a particle size of less than 200 mesh is ≥90%.

[0077] The material after the first ball milling is then subjected to a second ball milling process until the proportion of material with a particle size of less than 400 mesh is ≥95%.

[0078] Limiting the fineness of the first-stage ball milling (≥90% of the particles are -200 mesh) ensures that the roasted concentrate achieves initial dissociation, breaks down the oxide agglomeration structure, and exposes most of the gold particles initially, laying the foundation for the deep dissociation in the second-stage ball milling.

[0079] Limiting the fineness of the two-stage ball milling (≥95% of the particles are -400 mesh) can achieve complete dissociation of gold particles, maximize the contact area between gold particles and leaching agent, ensure the sufficiency of subsequent leaching reactions, and avoid increased energy consumption caused by over-grinding.

[0080] In some embodiments, the amount of the composite leaching agent is 55-65 kg / t dry ore;

[0081] The leaching treatment is performed at a temperature of 20–30°C for 20–28 hours.

[0082] Limiting the ball mill slurry concentration (40-50%) balances the contact efficiency between the material and the leaching agent and the slurry's fluidity. This ensures that the leaching agent can fully surround the solid particles while facilitating the mixing and transport of the slurry, thus providing a suitable material environment for the leaching reaction.

[0083] The limited leaching temperature (20-30℃) provides a stable reactive environment for the components of the composite gold leaching agent, eliminating the need for additional heating energy consumption. At the same time, it ensures the efficient progress of complexation and catalytic reactions, achieving a balance between energy saving and high efficiency.

[0084] Limiting the leaching pH (10.5–11.5) can stabilize the chemical properties of ammonium thiosulfate, prevent its hydrolysis and decomposition, and optimize the catalytic activity of copper ions, providing suitable acid-base conditions for the synergistic effect of the composite leaching agent.

[0085] The dosage of the composite gold leaching agent (55-65 kg / t dry ore) is matched with the gold content and material characteristics in the ball mill slurry to ensure that the effective components of the leaching agent are sufficient to completely complex and dissociate the gold ions, thus ensuring the stability and high efficiency of the leaching rate.

[0086] Limiting the leaching time (20-28h) provides sufficient kinetic conditions for the leaching reaction, ensuring that the composite gold leaching agent and gold particles complete the entire process of penetration, cleaning, catalysis, oxidation, and complexation, thereby maximizing the dissolution and transfer of gold.

[0087] Precious liquor grade (4.0~4.5g / t) and leaching residue grade (0.15~0.17g / t): This index system directly reflects the final effect of the leaching process. The high grade of the precious liquor ensures the effective enrichment of gold, while the low grade of the leaching residue indicates that the gold leaching rate has reached a high level, realizing the efficient recovery of resources.

[0088] The solution provided in this application has multiple advantages, the core of which stems from the precise targeting of process design and the systematic synergy of technical solutions. All of these advantages are directly driven by underlying process logic and key technological innovations.

[0089] The significant improvement in leaching rate is fundamentally due to the precise design of the entire chain: "structural modification - complete dissociation - efficient complexation". Mild oxidative roasting, through precise control of temperature and oxygen concentration, completely destroys the micro-particle encapsulation structure of gold, generating a porous and loose oxide carrier, creating the conditions for gold exposure; two-stage ball milling achieves graded dissociation based on the characteristics of the roasting product, ensuring that gold particles are completely freed from the carrier; and the composite gold leaching agent, through multi-component synergy, achieves deep penetration of the agent, cleaning of the gold surface, efficient catalytic oxidation, and stable complexation, allowing the exposed gold particles to be fully transformed into water-soluble complexes. Compared with the single processing logic of conventional processes and the limitations of direct leaching without pretreatment, this synergistic system significantly improves the gold extraction efficiency.

[0090] The excellent calcination stability and absence of secondary encapsulation are attributed to the precise control capabilities of the continuous suspension calcination system and the scientific adaptation of a mild oxidation strategy. The system maintains a stable fluidization state and oxidizing atmosphere through precise proportioning of loosening and fluidizing air flow, ensuring uniform heating and consistent reaction of the material. The mild calcination temperature of 480–520℃ avoids sintering or the formation of dense oxides caused by high temperatures, while also fully decomposing fine particles, fundamentally preventing secondary gold encapsulation. This results in minimal fluctuations in the leaching rate during continuous 24-hour operation.

[0091] The key to achieving complete gold encapsulation lies in the precise control of reaction conditions and the optimization of the reaction environment during the roasting process. The setting of a mild oxidation window perfectly matches the thermodynamic requirements of fine particle decomposition, while simultaneously suppressing ineffective side reactions. The continuous suspension roasting system ensures sufficient contact between the material and the gas, guaranteeing that each particle undergoes a complete oxidation process, ultimately achieving a gold encapsulation decomposition rate of ≥90%. This allows the gold in the roasted concentrate to exist primarily in an exposed state, clearing structural obstacles for subsequent leaching.

[0092] The effective cost reduction stems from the dual optimization of energy and reagent consumption in the process. The calcination temperature is 100-200℃ lower than that of conventional processes, directly reducing heat energy consumption. Combined with the high efficiency of continuous production, this results in a 20-30% reduction in energy consumption. The composite immersion gold agent is precisely formulated with optimized dosages and complementary functions of each component, avoiding ineffective consumption. At the same time, some reagents can be recycled, reducing the input of fresh reagents. Combined with the reduction in energy consumption, this ultimately achieves a 15-20% reduction in overall costs.

[0093] The core of achieving environmental and safety advantages lies in the comprehensive application of environmentally friendly technical solutions. The composite leaching agent replaces traditional highly toxic cyanide, eliminating the safety and environmental hazards posed by cyanide at the source. Simultaneously, the mild roasting and leaching conditions throughout the process reduce the generation of harmful byproducts. After processing, the heavy metal leaching concentration of the leaching residue meets the GB5085.3-2007 standard, ensuring a risk-free production process and achieving green gold extraction.

[0094] The high adaptability stems from the flexibility of process parameters and the universal design of core technologies. Key process parameters (such as roasting temperature, oxygen concentration, and gold leaching agent dosage) are all set with scientifically reasonable adjustable ranges. With slight adjustments, they can be adapted to low-grade and fine-grained gold ores with different gold-sulfur ratios and different encapsulation types. The structural modification logic of mild roasting, the dissociation strategy of two-stage ball milling, and the synergistic mechanism of composite gold leaching agents can address the core extraction pain points of different ores, ensuring that the leaching rate of various adapted ores is not less than 83%.

[0095] In summary, the core advantages of this application lie in three dimensions: the systematic nature of the process design, the targeted nature of the technological innovation, and the practicality of the application implementation, forming a gold extraction solution that balances efficiency, stability, and economy.

[0096] At the process design level, this application constructs a collaborative system encompassing "structural modification - precise dissociation - efficient extraction - separation and enrichment," with each stage closely linked and functionally complementary. The roasting pretreatment stage, through targeted atmosphere and temperature control, fundamentally disrupts the gold encapsulation structure of fine particles, rather than simply decomposing them, laying a crucial structural foundation for subsequent operations. The two-stage ball milling employs a graded dissociation strategy based on the characteristics of the roasted product, ensuring full exposure of gold particles while avoiding ineffective energy consumption. The leaching and separation stages precisely match the state of the upstream materials, achieving efficient gold conversion and rapid enrichment. The entire process has no redundant steps, forming a closed-loop optimization from raw materials to product.

[0097] At the technological innovation level, the core advantage lies in the synergistic innovation of mild oxidation technology and composite immersion gold agent. The low-temperature, oxygen-deficient, and precise control mode adopted in the roasting stage not only achieves effective decomposition of fine particles but also avoids secondary encapsulation or material sintering problems, taking into account both structural modification and resource protection. The composite immersion gold agent, through multi-component functional coupling design, integrates multiple functions such as penetration, cleaning, catalysis, complexation, and stabilization, achieving comprehensive coverage of the agent's effects on porous materials. This solves the pain points of insufficient penetration, poor stability, and weak synergy of traditional immersion gold agents, making the chemical extraction process more efficient and controllable.

[0098] At the application level, this application possesses significant practical value and economic advantages. The entire process does not require harsh conditions such as high temperature and high pressure; the combination of ambient temperature leaching and a continuous roasting system reduces equipment investment and energy costs. It has broad raw material adaptability, capable of processing fine-grained gold concentrates of different grades and related mixtures, thus expanding its application scenarios. The entire process is stable and controllable, with scientifically designed parameters at each stage, ensuring the stability of the leaching effect and facilitating large-scale industrial application. Simultaneously, it avoids resource waste and environmental pressure caused by over-processing, achieving a balance between efficient gold extraction and green production.

[0099] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed. Example 1

[0100] This embodiment provides a process for enriching, roasting, and leaching low-grade gold encapsulated in heavy media. The specific steps are as follows: S1, Roasting Pretreatment: A sulfide-encapsulated fine-particle gold concentrate with a grade of 0.98 g / t is fed into a continuous suspension roasting system for suspension roasting. The continuous suspension roasting system includes a feed hopper, a loss-in-weight weigher, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system. The roasting temperature is controlled at 500℃, and the oxygen concentration is 10%; the nitrogen flow rate of the reactor loosening air is controlled at 2.1 m³ / t. 3 / h, air flow rate is 1.9m 3 / h; The nitrogen flow rate for controlling the fluidizing air is 3.7m³ / h. 3 / h, airflow rate is 3.3m 3 / h; the feed rate is controlled at 20kg / h. After roasting, roasted concentrate is obtained with a grade of 1.13g / t and a loss on ignition rate of 6.30%.

[0101] S2. Grinding Process: The roasted concentrate is subjected to two-stage ball milling: First, the roasted concentrate is ball-milled until the proportion of material with a particle size of less than 200 mesh is 95.86%; then, the material after the first-stage ball milling is ball-milled again until the proportion of material with a particle size of less than 400 mesh is 96.54%. The grinding concentration is controlled at 50% during the ball milling process to obtain the ball-milled slurry.

[0102] S3. Leaching Treatment: The ball-milled ore slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 45%, the temperature at 25℃, and the pH at 11. A composite leaching agent is used at a dosage of 60 kg / t dry ore to leach the slurry for 24 hours to obtain the leached ore slurry. The composite leaching agent consists of the following components by weight: ammonium thiosulfate 55 parts, urea 12 parts, copper sulfate 2 parts, sodium dodecyl sulfate 0.3 parts, and citric acid 10 parts. During the leaching process, CaO is added to adjust the pH at a dosage of 30 kg / t dry ore.

[0103] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 4.38 g / t, and the grade of leaching residue is 0.166 g / t.

[0104] Calculations show that the overall gold leaching rate of the roasting-leaching process in this embodiment reaches 85.31%. Example 2

[0105] This embodiment provides a process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media, with the specific steps as follows:

[0106] S1. Roasting Pretreatment: A fine-grained gold concentrate with a grade of 0.96 g / t containing sulfides is fed into a continuous suspension roasting system for suspension roasting. The roasting temperature is controlled at 480℃, and the oxygen concentration at 8%; the nitrogen flow rate of the reactor aeration air is controlled at 2.0 m³ / t. 3 / h, air flow rate is 1.8m 3 / h; The nitrogen flow rate for controlling the fluidizing air is 3.6m³ / h. 3 / h, air flow rate is 3.2m 3 / h; the feed rate is controlled at 18kg / h. After roasting, roasted concentrate is obtained with a grade of 1.11g / t and a loss on ignition rate of 5.8%.

[0107] S2. Grinding Process: The roasted concentrate is subjected to two-stage ball milling: First, the roasted concentrate is ball-milled in one stage until 90% of the material has a particle size of less than 200 mesh; then, the material after the first stage ball milling is ball-milled in another stage until 95% of the material has a particle size of less than 400 mesh. The grinding concentration is controlled at 50% during the ball milling process to obtain the ball-milled slurry.

[0108] S3. Leaching Treatment: The ball-milled ore slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 40%, the temperature at 20℃, and the pH at 10.5. A composite leaching agent is used at a dosage of 55 kg / t dry ore to leach the slurry for 20 hours to obtain the leached ore slurry. The composite leaching agent consists of the following components by weight: ammonium thiosulfate 45 parts, urea 8 parts, copper sulfate 1 part, sodium dodecyl sulfate 0.05 parts, and citric acid 5 parts. During the leaching process, CaO is added to adjust the pH value at a dosage of 28 kg / t dry ore.

[0109] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 4.0 g / t, and the grade of leaching residue is 0.15 g / t.

[0110] Calculations show that the overall gold leaching rate of the roasting-leaching process in this embodiment reaches 83.5%. Example 3

[0111] This embodiment provides a process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media, with the specific steps as follows:

[0112] S1. Roasting Pretreatment: A sulfide-coated fine-particle gold concentrate with a grade of 1.0 g / t is fed into a continuous suspension roasting system for suspension roasting. The roasting temperature is controlled at 520℃, and the oxygen concentration is 12%; the nitrogen flow rate of the reactor aeration air is controlled at 2.2 m³ / t. 3 / h, air flow rate is 2.0m 3 / h; The nitrogen flow rate for controlling the fluidizing air is 3.8m³ / h. 3 / h, airflow rate is 3.4m 3 / h; the feed rate is controlled at 22kg / h. After roasting, roasted concentrate is obtained with a grade of 1.15g / t and a loss on ignition rate of 6.8%.

[0113] S2. Grinding Process: The roasted concentrate is subjected to two-stage ball milling: First, the roasted concentrate is ball-milled in one stage until 92% of the material has a particle size of less than 200 mesh; then, the material after the first stage ball milling is ball-milled in another stage until 97% of the material has a particle size of less than 400 mesh. The grinding concentration is controlled at 50% during the ball milling process to obtain the ball-milled slurry.

[0114] S3. Leaching Treatment: The ball-milled slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 50%, the temperature at 30℃, and the pH at 11.5. A composite leaching agent is used at a dosage of 65 kg / t dry ore to leach the slurry for 28 hours to obtain the leached slurry. The composite leaching agent consists of the following components by weight: ammonium thiosulfate 65 parts, urea 15 parts, copper sulfate 4 parts, sodium dodecyl sulfate 0.5 parts, and citric acid 15 parts. During the leaching process, CaO is added to adjust the pH at a dosage of 32 kg / t dry ore.

[0115] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 4.5 g / t, and the grade of leaching residue is 0.17 g / t.

[0116] Calculations show that the overall gold leaching rate of the roasting-leaching process in this embodiment reaches 84.8%. Example 4

[0117] This embodiment provides a process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media, with the specific steps as follows:

[0118] S1. Roasting Pretreatment: Fine-grained gold concentrate with a grade of 0.97 g / t is fed into a continuous suspension roasting system for suspension roasting. The roasting temperature is controlled at 490℃, and the oxygen concentration at 9%; the nitrogen flow rate of the reactor aeration air is controlled at 2.05 m³ / t. 3 / h, air flow rate is 1.85m 3 / h; The nitrogen flow rate for controlling the fluidizing air is 3.65m³ / h. 3 / h, air flow rate is 3.25m 3 / h; the feed rate was controlled at 19 kg / h. After roasting, roasted concentrate was obtained with a grade of 1.12 g / t and a loss on ignition rate of 6.1%.

[0119] S2. Grinding Process: The roasted concentrate is subjected to two-stage ball milling: First, the roasted concentrate is ball-milled in one stage until 94% of the material has a particle size of less than 200 mesh; then, the material after the first stage ball milling is ball-milled in another stage until 96% of the material has a particle size of less than 400 mesh. The grinding concentration is controlled at 50% during the ball milling process to obtain the ball-milled slurry.

[0120] S3. Leaching Treatment: The ball-milled slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 43%, the temperature at 23℃, and the pH at 10.8. A composite leaching agent is used at a dosage of 58 kg / t dry ore to leach the slurry for 22 hours to obtain the leached slurry. The composite leaching agent consists of the following components by weight: 50 parts ammonium thiosulfate, 10 parts urea, 2.5 parts copper sulfate, 0.2 parts sodium dodecyl sulfate, and 8 parts citric acid. During the leaching process, CaO is added to adjust the pH at a dosage of 29 kg / t dry ore.

[0121] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 4.2 g / t, and the grade of leaching residue is 0.16 g / t.

[0122] Calculations show that the overall gold leaching rate of the roasting-leaching process in this embodiment reaches 84.2%.

[0123] Comparative Example 1

[0124] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0125] S1. Roasting Pretreatment: A fine-grained gold concentrate with a grade of 0.98 g / t is fed into a continuous suspension roasting system for suspension roasting. The continuous suspension roasting system includes a feed hopper, a loss-in-weight weigher, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system. The roasting temperature is controlled at 650℃, and the oxygen concentration is 10%; the nitrogen flow rate for loosening the reactor air is controlled at 2.1 m³ / t. 3 / h, air flow rate is 1.9m 3 / h; The nitrogen flow rate for controlling the fluidizing air is 3.7m³ / h. 3 / h, airflow rate is 3.3m 3 / h; the feed rate is controlled at 20kg / h. After roasting, roasted concentrate is obtained with a grade of 1.10g / t and a loss on ignition rate of 12.5%.

[0126] S2. Grinding process: Same as in Example 1, to obtain ball mill slurry.

[0127] S3. Leaching treatment: Same as in Example 1, to obtain leached slurry.

[0128] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.25 g / t, and the grade of leaching residue is 0.28 g / t.

[0129] Calculations show that the overall gold leaching rate of this comparative process is 74.7%.

[0130] Comparative Example 2

[0131] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0132] S1. Roasting Pretreatment: A fine-grained gold concentrate with a grade of 0.98 g / t is fed into a continuous suspension roasting system for suspension roasting. The continuous suspension roasting system includes a feed hopper, a loss-in-weight weigher, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system. The roasting temperature is controlled at 500℃, and the oxygen concentration at 5%; the nitrogen flow rate for loosening the reactor air is controlled at 2.5 m³ / t. 3 / h, air flow rate is 1.2m 3 / h; control the nitrogen flow rate of the fluidizing air to 4.0m³ / h. 3 / h, air flow rate is 2.8m 3 / h; the feed rate is controlled at 20kg / h. After roasting, roasted concentrate is obtained with a grade of 1.08g / t and a loss on ignition rate of 4.2%.

[0133] S2. Grinding process: Same as in Example 1, to obtain ball mill slurry.

[0134] S3. Leaching treatment: Same as in Example 1, to obtain leached slurry.

[0135] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.10 g / t, and the grade of leaching residue is 0.31 g / t.

[0136] Calculations show that the overall gold leaching rate of this comparative process is 71.3%.

[0137] Comparative Example 3

[0138] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0139] S1. Roasting pretreatment: Same as in Example 1, to obtain roasted concentrate with a grade of 1.13 g / t and a loss on ignition rate of 6.30%.

[0140] S2. Grinding Process: The roasted concentrate is subjected to two-stage ball milling: the first stage ball milling is performed to -200 mesh (95.86%); the second stage ball milling is performed to -400 mesh (88%). The grinding concentration is controlled at 50% during the ball milling process to obtain the ball milled slurry.

[0141] S3. Leaching treatment: Same as in Example 1, to obtain leached slurry.

[0142] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.52 g / t, and the grade of leaching residue is 0.24 g / t.

[0143] Calculations show that the overall gold leaching rate of this comparative process is 78.8%.

[0144] Comparative Example 4

[0145] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0146] S1. Roasting pretreatment: Same as in Example 1, to obtain roasted concentrate with a grade of 1.13 g / t and a loss on ignition rate of 6.30%.

[0147] S2. Grinding process: Same as in Example 1, to obtain ball mill slurry.

[0148] S3. Leaching Treatment: The ball-milled slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 45%, the temperature at 25℃, and the pH at 11. A composite leaching agent is used at a dosage of 60 kg / t dry ore to leach the slurry for 24 hours to obtain the leached slurry. The composite leaching agent consists of: 55 parts ammonium thiosulfate, 12 parts urea, 2 parts copper sulfate, and 0.3 parts sodium dodecyl sulfate. During the leaching process, CaO is added to adjust the pH value at a dosage of 30 kg / t dry ore.

[0149] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.68 g / t, and the grade of leaching residue is 0.22 g / t.

[0150] Calculations show that the overall gold leaching rate of this comparative process is 80.5%.

[0151] Comparative Example 5

[0152] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0153] S1. Roasting pretreatment: Same as in Example 1, to obtain roasted concentrate with a grade of 1.13 g / t and a loss on ignition rate of 6.30%.

[0154] S2. Grinding process: Same as in Example 1, to obtain ball mill slurry.

[0155] S3. Leaching Treatment: The ball-milled slurry was fed into an 8-tank continuous leaching tank. The slurry concentration was controlled at 45%, the temperature at 25°C, and the pH at 9.0. A composite gold leaching agent was used at a dosage of 60 kg / t dry ore to leach the slurry for 24 hours to obtain the leached slurry. The composition and dosage of the composite gold leaching agent were the same as in Example 1. During the leaching process, CaO was added to adjust the pH value, with a CaO dosage of 15 kg / t dry ore.

[0156] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.36 g / t, and the grade of leaching residue is 0.26 g / t.

[0157] Calculations show that the overall gold leaching rate of this comparative process is 77.0%.

[0158] Comparative Example 6

[0159] This comparative example provides a process for enriching, roasting, and leaching low-grade encapsulated gold in a heavy medium. The specific steps are as follows:

[0160] S1. Roasting pretreatment: Same as in Example 1, to obtain roasted concentrate with a grade of 1.13 g / t and a loss on ignition rate of 6.30%.

[0161] S2. Grinding process: Same as in Example 1, to obtain ball mill slurry.

[0162] S3. Leaching Treatment: The ball-milled slurry is fed into an 8-tank continuous leaching tank. The slurry concentration is controlled at 45%, the temperature at 25℃, and the pH at 11. A composite leaching agent is used at a dosage of 60 kg / t dry ore to leach the slurry for 24 hours to obtain the leached slurry. The composite leaching agent consists of: 55 parts ammonium thiosulfate, 12 parts urea, 2 parts copper sulfate, and 10 parts citric acid. During the leaching process, CaO is added to adjust the pH value at a dosage of 30 kg / t dry ore.

[0163] S4. Solid-liquid separation: The leaching pulp is subjected to solid-liquid separation to obtain precious solution and leaching residue. The grade of precious solution is 3.75 g / t, and the grade of leaching residue is 0.21 g / t.

[0164] Calculations show that the overall gold leaching rate of this comparative process is 81.4%.

[0165] The process performance of Examples 1-4 and Comparative Examples 1-6 is summarized in Table 1.

[0166] Table 1. Comparison of process performance between Examples 1-4 and Comparative Examples 1-6

[0167]

[0168] As can be seen from the data in Table 1, the performance of the embodiments of this application differs significantly from that of the comparative examples, clearly demonstrating the rationality and superiority of the process design of this application.

[0169] From the performance of the embodiments, the process parameters (roasting temperature, oxygen concentration, grinding fineness, leaching conditions) of all embodiments are strictly controlled within the range defined in the claims, and the composite gold leaching agent components are complete, thus exhibiting stable and excellent comprehensive performance: the roasted concentrate grade is concentrated in 1.11 to 1.15 g / t, reflecting the effective enrichment of gold by mild roasting; the loss on ignition rate is maintained at a low level of 5.8% to 6.8%, without excessive oxidation or sintering; the leaching residue grade is only 0.15 to 0.17 g / t, and the precious liquor grade reaches 4.0 to 4.5 g / t, corresponding to a comprehensive gold leaching rate of over 83.5%, among which the optimal parameter combination of Embodiment 1 achieves the highest leaching rate of 85.31%. This result stems from the synergistic effect of parameters throughout the entire “roasting-grinding-leaching” process: gentle roasting fully destroys the micro-particle encapsulation structure, two-stage ball milling ensures complete dissociation of gold particles, a complete composite gold leaching agent achieves efficient complexation, and precise leaching conditions ensure stable reaction. Each step forms a closed-loop optimization, jointly promoting the simultaneous improvement of gold leaching rate and process stability.

[0170] Based on the performance analysis of the comparative examples and the reasons for their failures, all comparative examples showed significantly inferior performance compared to the original examples due to excessive core parameters or lack of key components. The specific reasons are as follows:

[0171] In Comparative Example 1, the roasting temperature was increased to 650℃ (exceeding the range of 480-520℃). The high temperature caused the ore to sinter and the gold to be encapsulated twice. This not only slightly reduced the grade of the roasted concentrate (1.10 g / t), but also caused the loss on ignition rate to soar to 12.5%. The gold particles had difficulty contacting the leaching agent, and the final leaching rate was only 74.7%.

[0172] Comparative Example 2 reduced the oxygen concentration during roasting to 5% (below the lower limit of 8-12%). The insufficient oxidizing atmosphere led to incomplete decomposition of finely encapsulated gold particles. The grade of the roasted concentrate (1.08 g / t) and the loss on ignition (4.2%) were both below ideal levels. The unexposed gold could not be effectively leached, with a leaching rate of only 71.3%.

[0173] In Comparative Example 3, the two-stage ball milling fineness was only 88% (not meeting the requirement of ≥95%-400 mesh), and the gold particles were not completely dissociated. Some gold was still encapsulated by the oxide carrier, resulting in the leaching residue grade rising to 0.24 g / t and the leaching rate dropping to 78.8%.

[0174] Comparative Example 4, due to the lack of citric acid component in the composite gold leaching agent, lost its interface modification and auxiliary catalytic functions, impurities on the gold surface could not be removed, the catalytic efficiency of copper ions decreased, the complexation reaction was hindered, and the leaching rate dropped to 80.5%.

[0175] The leaching pH of Comparative Example 5 was adjusted to 9.0 (below the range of 10.5-11.5). The insufficient weak alkaline environment led to a decrease in the stability of ammonium thiosulfate and a weakening of its complexing ability. The grade of the precious solution was only 3.36 g / t, and the leaching rate dropped to 77.0%.

[0176] In Comparative Example 6, due to the lack of sodium dodecyl sulfonate in the composite gold leaching agent, the surface tension of the solution could not be reduced, making it difficult to penetrate deep into the porous structure of the roasted concentrate. As a result, some fine gold particles failed to come into contact with the agent, and the leaching rate dropped to 81.4%.

[0177] In summary, the data in Table 1 clearly demonstrates that the process parameter range and the complete composition of the composite leaching agent defined in this application are key to achieving high leaching rate and high stability. Once these core designs are deviated from, it will directly lead to a significant decline in process performance, further confirming the creativity and necessity of the technical solution in this application.

[0178] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0179] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0180] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media, characterized in that, The process includes the following steps: S1. In a continuous suspension roasting system, fine-grained gold concentrate is suspended roasted at a roasting temperature of 480–520℃ and an oxygen concentration of 8–12% to obtain roasted concentrate. S2. The roasted concentrate is subjected to two-stage ball milling to obtain ball mill slurry; S3. Under the conditions of ball mill slurry concentration of 40-50%, temperature of 20-30℃ and pH of 10.5-11.5, the ball mill slurry is leached using a composite gold leaching agent to obtain leached slurry. The composite gold immersion agent, by mass, is composed of the following chemical components: 45-65 parts ammonium thiosulfate, 8-15 parts urea, 1-4 parts copper sulfate, 0.05-0.5 parts sodium dodecyl sulfonate, and 5-15 parts citric acid. The dosage of the composite gold leaching agent is 55-65 kg / t dry ore; The leaching treatment is performed at a temperature of 20–30°C for 20–28 hours.

2. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The grade of the fine-grained gold concentrate is 0.96–1.0 g / t.

3. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 2, characterized in that, The fine-grained encapsulated gold concentrate is a mixture of heavy media pre-enriched concentrate and heavy media separation tailings from the same ore, which have been ground to -0.5 mm. The grade of the heavy media pre-enriched concentrate is 1.04 to 1.08 g / t, and the heavy media separation tailings are low-density products obtained after heavy media separation.

4. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The continuous suspension roasting system includes a feeding hopper, a loss-in-weight scale, a suspension roasting furnace, a cyclone separator, a vertical cooler, and a dust collection system. The roasting atmosphere is maintained by controlling the loosening air and fluidizing air introduced into the suspension roasting furnace.

5. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 4, characterized in that, The nitrogen flow rate of the loosening air is 2.0–2.2 m³ / h. 3 / h, airflow rate is 1.8~2.0m 3 The nitrogen flow rate of the fluidizing air is 3.6–3.8 m³ / h. 3 / h, airflow rate is 3.2~3.4m 3 / h.

6. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The feed rate for suspension roasting is 18–22 kg / h.

7. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The grade of the roasted concentrate is 1.11-1.15 g / t, the loss on ignition is ≤10%, and the decomposition rate of the fine-grained gold concentrate is ≥90%.

8. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The two-stage ball milling includes: First, the roasted concentrate is ball-milled until the proportion of material with a particle size of less than 200 mesh is ≥90%. The material after the first ball milling is then subjected to a second ball milling process until the proportion of material with a particle size of less than 400 mesh is ≥95%.

9. The process for enriching, roasting, and leaching low-grade gold-encapsulated heavy media according to claim 1, characterized in that, The process also includes the following steps: S4. The leaching slurry is subjected to solid-liquid separation to obtain precious solution and leaching residue; The grade of the precious liquor is 4.0-4.5 g / t, and the grade of the leaching residue is 0.15-0.17 g / t.

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