Graphite Beneficiation Process

Crystalline graphite possesses excellent natural floatability; consequently, beneficiation is almost exclusively achieved through flotation methods. Since the size of the graphite flakes constitutes one of its most critical quality indicators, the separation strategy employs a process of multi-stage grinding and multi-stage flotation to facilitate the early recovery of large-flake graphite. The typical beneficiation flowsheet consists of one roughing stage, one scavenging stage, and seven to eleven cleaning stages, yielding a graphite concentrate with a fixed carbon content ranging from 90% to 97%.

Commonly used reagents in the flotation process include kerosene and diesel as collectors; “No. 2 Oil” and “No. 4 Oil” as frothers; lime and sodium carbonate as modifiers; and water glass (sodium silicate) as a depressant.

For graphite ores containing associated heavy minerals, a combined gravity separation and flotation flowsheet may be employed: gravity separation is utilized first to remove the heavy minerals, after which the gravity separation tailings (the lighter mineral fraction) are processed using flotation methods.

Cryptocrystalline graphite consists of extremely minute crystals—hence it is also referred to as microcrystalline graphite—and the graphite particles are frequently finely disseminated within a clay matrix, making their separation particularly challenging. Due to the high grade of the raw ore (typically containing 60%–80% carbon), many graphite mines directly crush and process the extracted ore to produce and sell graphite powder products.

A specific graphite mine in Hunan Province established a flotation plant in the 1950s to process cryptocrystalline graphite; however, operations were eventually suspended due to prohibitively high costs. Currently, various institutions continue to conduct research into novel flotation processes for cryptocrystalline graphite (such as oil agglomeration flotation).