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The gold ore dressing plants built in the early days generally adopted single or combined processes such as flotation, gravity separation, and amalgamation. Due to the limitations of the beneficiation technology at that time, the recovery rate was generally low, and a large amount of fine gold, encapsulated gold, or gold associated with specific minerals was lost to the tailings, causing huge economic losses.
Today, with the continuous upgrading and innovation of mineral processing technology, and with the widespread use of automated and intelligent equipment, we have the ability to turn the valuable elements in those old tailings into treasures, creating economic benefits for the beneficiation plant and laying the foundation for the sustainable development of the mining industry.
This article introduces the four commonly used processes for gold tailings reprocessing, as well as the procedures and steps involved in the reprocessing workflow.
In addition to precious metals such as gold and silver, gold tailings are also rich in valuable associated components such as lead, zinc, copper, and sulfur. Comprehensive recovery of these substances can improve the overall project benefits and is also a key approach to "squeezing out" resources and practicing the concept of green mining.
The following four processes are commonly used for gold tailings reprocessing:
1. Combined Magnetic Separation and Gravity Separation to Recover Iron
· Applicable tailings: Generally used for placer gold tailings, especially those rich in magnetic minerals such as magnetite, hematite, ilmenite, and garnet.
· Reprocessing process: This method mainly targets the characteristics of placer gold tailings rich in magnetic minerals. A high-gradient magnetic separator is used to separate the magnetite concentrate, followed by gravity separation equipment such as spiral chutes and shaking tables to enrich weakly magnetic minerals like hematite, ilmenite, and garnet.
For weakly magnetic mixed concentrates with complex compositions, magnetic roasting can be applied to convert hematite and siderite into strongly magnetic magnetite, which can then be recovered via magnetic separation.
2. Whole-Ore Cyanidation Method for Recovering Gold and Silver
· Applicable tailings: Tailings where gold exists as fine free particles, or oxidized/primary tailings in which inclusions can be dissociated under fine grinding conditions.
· Reprocessing process: The tailings are ground until full dissociation is achieved, then leached in a sodium cyanide solution, where gold dissolves to form a gold-cyanide complex. Activated carbon with a large specific surface area is used to adsorb the gold-cyanide complex (carbon adsorption). Finally, gold mud is obtained through desorption electrolysis and refined into doré gold.
· Process advantages: High technical maturity, simple process, stable recovery rate, and eliminates the costs associated with mining and crushing raw ore. Tailings treatment costs are significantly reduced. With a gold content of around 1 g/t, the tailings still hold high economic value.
3. Carbon Slurry Process: A Must for Low-Grade Gold Tailings
· Applicable tailings: Suitable for treating low-grade gold tailings with a gold grade of <1 g/t. The system offers excellent performance, stable returns, and reactivates low-grade stockpiled resources.
· Reprocessing process: The tailings are ground in a ball mill equipped with an intelligent control system to effectively prevent over-grinding. They are then stirred in an aerated agitation tank. Special activated carbon with high strength, strong adsorption capacity, and low wear rate is selected. Tailings solutions are treated using hydrogen peroxide oxidation (INCO process) or acid recovery (AVR process) to destroy residual cyanide and recover sodium cyanide, thereby significantly reducing environmental risk and reagent costs.
4. Flotation Method for Comprehensive Recovery of Sulfur and Gold-Bearing Sulfides
· Applicable tailings: Tailings containing mainly pyrite, with associated minerals such as chalcopyrite, bornite, native gold, electrum, and specularite, siderite, etc. The gangue is mainly quartz and sericite.
· Reprocessing process: A "one-stage grinding + priority flotation" process is adopted. First, tailings are ground to achieve monomer dissociation of target minerals, followed by flotation. During flotation, high-efficiency regulators and selective collectors are used to preferentially float copper minerals with high gold content. Then the reagent system is adjusted to float gold-bearing pyrite and obtain sulfur concentrate. For iron oxide minerals, strong magnetic separation can be applied after sulfur flotation.
· Process advantages: This process not only effectively recovers gold but also allows for the simultaneous recovery of copper concentrate, sulfur concentrate, and iron concentrate, achieving comprehensive resource utilization.
Developing a scientific and reasonable gold tailings reprocessing plan is the key to achieving economic benefits. Therefore, before formulating the reprocessing plan, a series of tasks need to be carried out, such as tailings property survey, process comparison, economic assessment, and environmental compliance, which are introduced separately below.
1. Tailings Property Survey
First, the target tailings must be systematically sampled. In this process, the mineral composition, chemical properties, physical properties, etc. of the tailings need to be analyzed. In addition, investigating historical production data is also very important.
2. Customized Process Design
The process design should strictly follow the principle of "one deposit, one solution", as there is no universal process. Therefore, rigorous laboratory tests must be conducted based on the characteristics of the tailings, target products, investment budget, and environmental protection requirements. In some cases, pilot-scale continuous tests are also necessary to compare technical routes and determine process parameters and equipment selection.
3. Economic Assessment
Cost estimation and market price forecasting are key to determining the feasibility of the project. Cost accounting includes reagent consumption, energy use, labor, equipment depreciation, and environmental protection investment.
The physical volume, spatial distribution, and transportation distance of the tailings also have a significant impact on processing scale and economic returns. Large and concentrated tailings ponds are considered ideal.
4. Environmental Considerations
When designing the cyanidation process, the "Technical Specifications for Pollution Control of Cyanide Residue in the Gold Industry" and other relevant regulations must be strictly followed. A complete tailings treatment system, seepage-proofing measures, and online monitoring systems should be implemented. Treatment plans for dust, noise, and ecological restoration must also be formulated.
Gold tailings reprocessing is a key pathway for comprehensive resource recovery, improving plant efficiency, and promoting the sustainable development of the mining industry. Xinhai Mining has been deeply involved in the field of mineral processing for 27 years and is well versed in every aspect of "mining, beneficiation, and tailings management." So far, it has served more than 2,500 mines, with projects in over 100 countries and regions around the world. We have accumulated a wealth of successful experience in handling complex projects both domestically and internationally.
In terms of gold tailings reprocessing, Xinhai can not only provide the four reprocessing technologies mentioned above, but also offer advanced equipment, a professional R&D and engineering team, and one-stop solutions. We are committed to converting the potential value in tailings into economic benefits. If you have any needs related to gold tailings reprocessing, please contact us.
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