Mineralogical Characteristics: Why Flotation Failed
Understanding the ore's nature is key to selecting the right process. The ore is primarily sericitized altered rock and sulfide-poor quartz vein type. Key characteristics include:
Gold Occurrence: 93.85% of gold is associated with gangue (quartz), only 6.15% with pyrite/limonite.
Particle Size: Extremely fine (<0.037mm) and unevenly distributed.
Low Sulfide Content: Makes traditional flotation difficult.
The Challenge: Flotation tests (one roughing, two scavenging) yielded poor results. Even at an optimal grind of -0.074mm (65%), the recovery rate was only 46.41%. This confirms the ore is "difficult to float" due to the lack of sulfide association.
Solution: CIP/CIL PANDA Gold-Dissolving Agent
Given the low levels of harmful elements (As, Cu) and the simple ore composition, the FKN environmentally friendly gold-dissolving agent was identified as the most suitable alternative to cyanide.
We conducted three primary tests to determine the optimal process flow:
1. CIP/CIL Cyanide-Free Leaching Test
Performed under a pulp concentration of 33%, this test showed promising lab-scale results:
Grind Size: -0.074mm accounting for 95%.
Recovery Rate: Achieved 85.71% leaching rate.
Note: While effective, the high grinding cost made direct transportation to the central plant (5km away) economically unfeasible.
2. Heap Leaching Test: The Economic Winner
To reduce costs, an on-site heap leaching trial was conducted. The process involved:
Pile Building: Mixing 10kg samples with quick lime (6kg/t).
Alkali Washing: Pre-wetting until pH 10 was reached.
Leaching Cycle: Spraying FKN reagent at varying concentrations (0.10% initial, 0.05-0.08% mid, 0.03-0.05% final).
3. Heap Leaching Results Comparison
The following table summarizes the heap leaching performance:
| Test No. | Quick Lime Usage (kg/t) | NaOH Usage (kg/t) | Leaching Rate (%) |
|---|---|---|---|
| 1 | 6 | 0.8 | 70.2 |
| 2 | 7 | 0 | 56.97 |
Conclusion: Using NaOH flake alkaline water instead of lime water during the washing phase significantly boosted the recovery rate to 70.2%.
Industrial Application & Waste Management
Based on the test results, the recommended industrial process is on-site heap leaching.
Annual Throughput: ~60,000 tons.
Expected Output: ~10kg of gold annually.
Environmental Compliance: Tailings & Waste Liquid Treatment
Safety is paramount. The process includes strict protocols for detoxification:
Sprinkle calcium hypochlorite on the ore pile surface.
Spray with clean water.
Discharge Standard: When the return liquid CN- concentration is <0.5 ppm, it meets the detoxification standard.
After treatment, the residue can be transported to the slag discharge warehouse, and the liquid can be discharged directly.
Related Catalogues:
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GOLD RECOVERY OPTIMIZATION SYSTEM
FAQ for Mineralogical Characteristics: Why Flotation Failed
1. Why was flotation rejected for this oxide gold ore?
Flotation was deemed unfeasible due to the ore's mineralogy. In this specific Tonghua Hengbang case, 93.85% of the gold is associated with gangue (quartz) rather than sulfide minerals like pyrite. The fine particle size (<0.037mm) and lack of sulfidation resulted in a low recovery rate of only 46.41%, making the process economically unviable.
2. What is the advantage of using the PANDA gold-dissolving agent over traditional cyanide?
The PANDA agent is an eco-friendly alternative suitable for ores with low harmful elements (like As and Cu, which are minimal in this ore). It allows for effective gold dissolution without the severe environmental risks associated with cyanide, while still achieving a high leaching rate (up to 85.71% in lab full-mud tests).
3. Why was on-site heap leaching chosen instead of central plant processing?
Two main factors dictated this decision: Cost and Ore Characteristics. The ore pile is located 5km from the main plant, making transportation costly. Additionally, the ore is "seriously muddy," which would disrupt the control and indicators of the central plant's flotation circuit. On-site heap leaching eliminates transport costs and handles the mud issue effectively.
4. How does alkali type affect the heap leaching efficiency?
The test data shows a significant difference. Using NaOH (Sodium Hydroxide) flake alkaline water instead of standard lime water during the alkali-washing phase increased the gold leaching rate from 56.97% to 70. Abstract 2%. This suggests better pH control or reduced passivation of the ore surface with NaOH.
5. What is the detoxification protocol for the leaching residue?
To ensure environmental safety post-leaching, calcium hypochlorite is sprinkled on the pile surface and sprayed with water. The residue is only discharged when the return liquid's cyanide ion (CN-) concentration drops below 0.5 ppm