Graphite has excellent natural floatability and is generally collected using flotation with neutral oil. The following points should be noted in flotation:

(1) Types of graphite ore. Graphite ore is divided into flake graphite ore and earthy graphite ore. Flake graphite ore is characterized by graphite in flake or leaf-like shapes. The grade of the raw ore is not high, generally between 3% and 5%, and at most 20% to 25%. This type of graphite has good floatability, and after flotation, the grade can reach over 90%. Therefore, a raw ore grade of 2% to 3% is sufficient for mining. Flake graphite has excellent properties and can generally be used to manufacture high-grade carbon products. Earthy graphite, also known as cryptocrystalline graphite ore, has small graphite crystals (generally less than 1 μm), an earthy surface, and lacks luster. Its industrial performance is inferior to that of flake graphite. The raw grade of this type of graphite ore is relatively high, generally between 60% and 80%, but its floatability is very poor. After flotation, the grade will not significantly improve. Therefore, raw ore with a grade less than 65% is generally not mined, while ore with a grade between 65% and 80% can be utilized after beneficiation. Therefore, for graphite ore, one should not only consider its raw ore grade, but also first clarify its type before deciding whether to adopt a flotation scheme.

(2) Care should be taken to protect large flakes during the beneficiation process. Large flake graphite has wide applications, is scarce, and has high value. Therefore, it is essential to protect the large flakes from breakage during production. Large flakes typically refer to +50 mesh, +80 mesh, and +100 mesh flake graphite. The measure to protect large flakes is to use a multi-grinding and multi-beneficiation process during beneficiation, promptly selecting the liberated graphite obtained from each grinding. Grinding the ore to a very fine particle size in one go will damage the large flakes. For example, the Nanshu Graphite Mine, a large graphite mine in my country, adopts a process of one roughing, one scavenging, four grinding, and six cleaning stages. This process protects the large flakes from damage and ensures a concentrate grade of 90%.

(3) High product grade requirements. High grade requirements are placed on graphite products. For example, ordinary flake graphite requires a grade of over 89%, pencil graphite requires 89%–98%, and some electro-carbon graphite requires a grade of up to 99%. To obtain high-grade graphite concentrate, the number of cleaning stages in graphite flotation is generally quite high.