This process design is conducted for gold recovery from copper tailings with a gold grade of 1.2 g/t. The process is comprehensively designed based on the occurrence state of gold, tailings particle size, associated minerals, environmental protection requirements and production economy. The following is the process flow configuration scheme based on industrial practice.
1. Analysis of Gold Occurrence State
When free gold particles are larger than 0.1 mm, gravity separation is preferentially adopted for gold recovery.
When gold occurs as sulfide-encapsulated particles, pre-treatment by flotation or leaching is required to liberate gold minerals.
When gold is encapsulated in copper oxide or iron minerals, roasting or acid leaching is used to break the mineral encapsulation and release gold.
2. Process Flow Configuration
Pre-treatment Stage (Dual Processes of Liberation + Desliming)
Re-grinding liberation and desliming are performed on copper tailings. Combined grinding by ball mill and vertical stirred ball mill is adopted to grind the tailings to a fineness of 65%–85% passing 0.074 mm, ensuring sufficient liberation of gold minerals from gangue.Hydrocyclones are used to remove slime smaller than 0.02 mm. Gold loss in this stage is controlled within 10%, which reduces reagent consumption in subsequent separation and avoids interference of slime on gold recovery.
Coarse Gold Recovery (Pre-concentration by Gravity Separation)
For liberated free coarse gold larger than 0.1 mm, a combined gravity separation process (spiral chute roughing + shaking table cleaning) is applied to pre-concentrate gold from low-grade copper tailings, recovering easy-beneficiated coarse gold in advance and improving the feed grade for subsequent processes.
Fine Gold Recovery (Flotation + Leaching)
After coarse gold recovery, fine gold and encapsulated gold in the tailings are recovered by flotation or leaching according to their occurrence states, so as to adapt to gold minerals with different refractoriness.
(1) Flotation Process (Suitable for Fine Gold Encapsulated in Sulfides)
Reagent regime: Butyl xanthate as collector, lime as regulator, and terpineol as frother;
The pulp pH is controlled at 8–9 with lime to depress pyrite and associated copper minerals in copper tailings, so as to reduce copper interference in gold recovery.
Flotation flowsheet: One roughing, two scavengings and two cleanings. Middlings are returned to the corresponding flotation cells in sequence for re-separation;
Flotation can produce gold concentrate with a grade of 15–58 g/t and a stable gold recovery rate of 60%–75%.
(2) Leaching Process (Suitable for Micro-fine Gold / Oxide-Encapsulated Gold / Refractory Gold)
For micro-fine gold unrecoverable by flotation, or refractory gold encapsulated in copper oxide and iron minerals, a combined roasting + flotation process is adopted for enhanced recovery:Roasting is firstly used to break the mineral encapsulation for full gold liberation, and then the liberated gold minerals are recovered by flotation to improve the overall gold recovery rate.
3.Copper Interference Control
When the copper content in copper tailings exceeds 0.3%, copper minerals will seriously interfere with gold separation, and copper removal must be carried out in advance:Pre-flotation with low-dosage collector is preferentially used to remove most copper minerals from tailings before gold separation;If leaching is adopted for gold recovery, thiosulfate leaching can be used instead of conventional cyanide leaching to avoid reagent waste and gold loss caused by the reaction between copper and cyanide;For cyanide leaching, cross-circulation of process water can be adopted to recover unreacted sodium cyanide in the pulp, so as to reduce reagent cost.
4.Micro-fine Gold Loss Control
Slime smaller than 0.02 mm in tailings tends to adsorb gold minerals, resulting in loss of micro-fine gold. Dual measures are required to control such loss:Enhance the desliming effect of hydrocyclones in the pre-treatment stage to reduce slime content at the source;If the slime content is high, dispersants can be added in the separation stage to desorb gold minerals from slime, or flocculants can be supplemented to recover micro-fine gold in slime, so as to further improve the comprehensive gold recovery rate.
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