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Not only used on photovoltaic panels
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SystemEco-Friendly Gold Extraction Solution for Gold Ore Beneficiation, Replacing the Traditional Cyanide Leaching Process
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PlaceShangluo, Shaanxi, China
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Date2024-12-01
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ApplicationEco-Friendly Gold Extraction Solution for Gold Ore Beneficiation, Replacing the Traditional Cyanide Leaching Process
Project background
This project was implemented at a private gold beneficiation enterprise in Shangluo, Shaanxi. The mining area is located within the Qinling ecological control zone and mainly processes quartz-vein oxidized gold ore. The plant has a daily ore processing capacity of 260 tons and an annual beneficiation capacity of 85,000 tons. For more than ten years, the mine had relied on the traditional sodium cyanide heap leaching process for gold extraction.
With the implementation of stricter ecological protection regulations in the Qinling region, regular environmental inspections, and tighter management of hazardous chemicals, the original production model gradually exposed multiple challenges.
From an environmental compliance perspective, cyanide is a highly toxic hazardous chemical. Its procurement, storage, transportation, and on-site use require strict hazardous chemical registration and management. Cyanide-containing wastewater and cyanide tailings must meet strict hazardous waste treatment requirements, resulting in rising tailings disposal costs and increasing wastewater detoxification costs. The cost of harmless treatment for each ton of tailings had exceeded RMB 100, placing continuous pressure on the mine’s environmental operation costs.
From a production perspective, the ore contained trace copper and arsenic impurities, which interfered with the traditional cyanide leaching process. The gold leaching rate remained around 81%–84% for a long time, while the residual gold grade in tailings stayed at about 0.38 g/t, causing valuable gold resources to be lost with tailings. In addition, the cyanide leaching cycle was long, with each heap leaching batch requiring about 42 days of spraying, limiting equipment turnover efficiency.
To meet green mining requirements, reduce policy-related shutdown risks, and improve recovery efficiency, the company began selecting a cyanide-free eco-friendly gold extraction reagent in the second half of 2024. After laboratory bottle tests and small-scale heap leaching comparisons with several reagent suppliers, the mine finally selected YINGCAI New Materials for phased replacement of the original cyanide-based production system.
Project introduction
The project was carried out in three stages: small-scale industrial testing, full-line reagent replacement, and on-site process optimization. YINGCAI New Materials assigned technical engineers to stay on site for 35 days, providing reagent commissioning, operating guidance, and data tracking. The project continued to use the mine’s existing heap leaching, spraying, and zinc powder replacement production lines, without requiring major equipment modification.
1. Pilot Test and Medium-Scale Trial Stage
A total of 5,200 tons of low-grade tailings were selected for the trial heap, with an average ore grade of 0.72 g/t. The crushed ore particle size was controlled between 15–70 mm. The existing HDPE anti-seepage membrane and spraying pipe network were used.
According to YINGCAI’s reagent application guidelines, lime was first added to adjust the leaching solution pH to 10.8–11.8. The reagent was dissolved and added in stages, with the prepared reagent concentration controlled at 0.12%. The reagent was added three times, with a total dosage of 1.08 kg per ton of ore.
The trial heap leaching cycle lasted 33 days, which was 9 days shorter than the original cyanide process. Samples were collected three times daily to monitor gold concentration in the leaching solution and residual gold in tailings. After the medium-scale trial, the measured gold leaching rate reached 89.2%, and the residual gold in tailings decreased to 0.27 g/t. After all indicators met expectations, the project moved to full-line replacement.
2. Full-Scale Industrial Application
During full-scale production, the mine retained its original heap leaching layout with a daily processing capacity of 260 tons. YINGCAI dynamically optimized the reagent formula according to annual changes in impurity content in the ore.
For ore batches with higher mud content during the rainy season or increased soluble copper content, a small amount of YINGCAI special leaching aid was used to reduce reagent consumption caused by impurities. For common oxidized ore, only the basic eco-friendly gold extraction agent was required.
The reagent no longer needed hazardous chemical warehouse storage and could be stored at room temperature in a regular raw material warehouse, without explosion-proof or leakage-proof special storage facilities. The wastewater treatment process also eliminated the hydrogen peroxide cyanide detoxification step. Production wastewater was treated through simple lime neutralization and sedimentation, then fully reused for heap spraying, achieving closed-loop circulation without external discharge.
3. Long-Term On-Site Operation Management
After stable production, YINGCAI established a monthly follow-up mechanism. The reagent dosage standard was adjusted monthly according to the mine’s ore testing report. On-site operators tested reagent concentration in the leaching tank every two hours and added reagent when the concentration fell below 80% of the benchmark value.
Throughout the year, YINGCAI supplied eco-friendly gold extraction reagent in six batches, meeting the mine’s annual beneficiation demand of 85,000 tons. The production process operated smoothly without shutdowns for process adjustment. The zinc powder replacement stage remained stable, and no decline in replacement efficiency caused by reagent impurity accumulation was observed.
Customer value
1. Environmental Compliance Value and Lower Policy Risk
After replacing the cyanide process, the tailings and wastewater treatment costs were significantly reduced. Since the reagent contains no cyanide or highly toxic components, the tailings are no longer classified as hazardous solid waste. The tailings treatment cost decreased from RMB 102 per ton to RMB 28 per ton. Based on an annual tailings volume of 85,000 tons, the mine saves approximately RMB 6.37 million in tailings treatment costs each year.
The wastewater no longer requires cyanide detoxification reagents such as hydrogen peroxide and bleaching powder, helping the company save more than RMB 720,000 per year in wastewater treatment consumables.
The mine also reduced safety and compliance costs. It no longer needs to purchase controlled hazardous chemicals or pay for cyanide transportation registration, hazardous chemical warehouse inspections, and annual certification for hazardous chemical operators. This also helps reduce safety risks related to cyanide leakage and poisoning. The project has supported the company in passing green mine inspections and environmental checks, with no rectification notice caused by excessive environmental indicators in recent years.
2. Production Efficiency and Economic Benefits
After full-line replacement, the comprehensive gold leaching rate increased from 82.6% to 88.7%. Based on an annual ore processing volume of about 85,000 tons and an average ore grade of 0.72 g/t, the mine can recover approximately 3,170 g more gold per year, creating additional output value of more than RMB 900,000 based on the domestic spot gold price.
The residual gold content in tailings decreased, enabling the company to reuse low-grade tailings that were previously difficult to process effectively. The mine has gradually activated more than 30,000 tons of old tailings for secondary heap leaching and additional revenue generation.
The average single-batch heap leaching cycle was shortened by 18%, increasing the number of effective heap leaching batches under the same site conditions and improving site utilization. Although the unit price of the eco-friendly reagent is higher than sodium cyanide, the total reagent consumption per ton of ore was optimized. After adding the savings in environmental compliance costs, the total reagent and environmental treatment cost per ton decreased by 7.3%, saving more than RMB 450,000 in annual beneficiation reagent costs.
3. Long-Term Sustainable Development Value
The project is aligned with Shaanxi’s industrial direction of restricting cyanide-based beneficiation and encouraging cyanide-free green mineral processing. When the company applies for mining license renewal and tailings expansion approval in the future, the cyanide-free process can become an advantage in environmental impact assessment approval, helping shorten approval cycles and improve approval efficiency.
The improved environmental process also expands the mine’s raw material procurement channels. The mine can purchase nearby scattered low-grade ores from small mining sites, broaden ore supply sources, and reduce fixed beneficiation costs per unit. At the same time, the on-site working environment has improved, reducing occupational health management pressure and helping stabilize the frontline workforce.
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1.Project background
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2.Project introduction
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3.Customer value
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