The Complete Process Flow of Gravity and Flotation Separation for Gold Ore

Gold ore separation is primarily based on the mineralisation characteristics of the ore; gravity separation and flotation are the two fundamental separation methods. As a single process is often insufficient to handle complex mineral phases, the combined gravity and flotation process has become the mainstream solution in the industry.

Gravity separation relies on the density difference between gold minerals and gangue to achieve separation. The overall process involves no chemical consumption, produces low levels of pollution, and features simple equipment design. It excels at processing coarse and medium-sized gold particles and offers significant advantages in energy consumption control. Its main limitation lies in its relatively low separation efficiency for fine-grained gold; it is therefore primarily used in the front-end stage for pre-enrichment to recover coarse, free gold. Conventional gravity separation equipment utilises the principles of centrifugation, hydrostatic stratification and gravitational settling to achieve separation. The entire process can function independently as the core recovery process for placer gold; in the beneficiation of rock gold, it is often employed as a preliminary auxiliary process to prioritise the liberation and recovery of exposed coarse gold, thereby reducing reagent consumption in subsequent flotation stages. Gravity separation produces high-grade gold concentrate, whilst the tailings are fed back into the grinding process to further liberate fine-grained gold-bearing minerals, thereby facilitating subsequent flotation operations.

Flotation is suitable for primary gold and associated sulphide-type gold ores, where gold is predominantly associated with sulphide host minerals such as pyrite, arsenopyrite and chalcopyrite. Sulphide minerals possess naturally good floatability, enabling the large-scale concentration of fine-grained gold into the sulphide concentrate. Floating relies on various reagents to adjust the hydrophilic and hydrophobic properties of mineral surfaces, separating gold-bearing minerals from gangue through mineralised froth. Recovery rates for primary sulphide ores are more stable, whilst separation indices for oxidised ores exhibit some fluctuation. Floating equipment is categorised into two types: air-suction agitation and air-injection agitation, with selection based on the processing capacity of the concentrator. A multi-stage floating process enables the production of gold concentrates of varying grades in batches, thereby enhancing the overall resource recovery rate.

Most gold-bearing ores are characterised by a mixed grain size distribution and complex mineral composition; efficient recovery cannot be achieved through gravity separation or flotation alone, and combined gravity-flotation separation processes are becoming increasingly widespread. The mainstream processes are divided into two modes: firstly, the gravity-first process, in which coarse-grained native gold is recovered via gravity separation, followed by grinding of the tailings and flotation to capture fine-grained gold-bearing sulphides; secondly, the flotation-first process, in which flotation produces a gold-bearing rough concentrate, followed by gravity separation to further refine the concentrate grade. Some polymetallic gold deposits also incorporate auxiliary processes such as magnetic separation to recover gold minerals in different forms through a multi-stage process.

The reagent systems for gravity separation and flotation have distinct focuses: gravity separation requires no addition of separation reagents, relying solely on water flow to control the separation effect; flotation relies on the synergistic action of collectors, inhibitors and activators to achieve separation. The two processes can be flexibly combined and adapted; the sequence of operations and operating parameters can be adjusted according to the grain size distribution, degree of oxidation and types of associated minerals in the ore, thereby enabling the simultaneous recovery of both coarse and fine-grained gold. This achieves a balance between mineral processing recovery rates and production costs, and meets the separation requirements for various types of rock gold, placer gold and associated gold ores.