Graphite Ore Beneficiation Technology: Processes and Reagents

Graphite, a strategic non-metallic resource with excellent electrical conductivity, thermal conductivity, and lubricity, is widely used in machinery, chemical engineering, new energy, and other fields. Natural graphite is classified by crystal size into large flake graphite (crystal size >150μm), fine flake graphite (crystal size <150μm), and microcrystalline graphite (crystal size <1μm). Beneficiation processes for different types of graphite vary due to differences in ore properties. Currently, flotation is the main method for graphite purification, focusing on optimizing grinding and flotation processes and reagent systems to achieve efficient separation of graphite from gangue minerals. 

Grinding and Flotation Processes for Different Graphite Types

Large Flake Graphite: Balancing Flake Protection and Efficient Separation

Due to its high economic value, the key to large flake graphite beneficiation is to improve recovery while protecting flake integrity. A stage grinding and flotation process is commonly used: after one stage of rough grinding and roughing, the rough concentrate undergoes 3-5 stages of regrinding and 5-7 stages of cleaning, with staged collection of large flakes to avoid damage from over-grinding. To enhance flake protection, improved technologies have been developed, such as rapid flotation (prioritizing recovery of large flakes using differences in flotation rates between monomers and aggregates) and classified grinding and flotation (targeted treatment of different particle sizes after sieving). For example, a flake graphite ore in Shandong using rapid flotation achieved a concentrate fixed carbon content of 91.89%, recovery of 92.52%, and the yield of +0.30mm large flakes increased by 10.74 percentage points compared to conventional processes.

Fine Flake Graphite: Sufficient Liberation and Deep Purification

Fine flake graphite does not require emphasis on flake protection; the core of the process is to achieve sufficient mineral liberation. A typical 流程 involves "1 rough grinding - 1 roughing - 1 scavenging, with multiple stages of regrinding and cleaning for rough concentrates". For instance, a low-grade fine flake graphite ore in Hubei, after 3 regrinding stages and 6 cleaning stages, saw its concentrate fixed carbon content increase from 4.30% to 90.17% with a recovery of 90.38%. A fine flake graphite ore in Australia, through 4 regrinding stages and 5 cleaning stages, achieved a concentrate fixed carbon content of 90.50% and a recovery of 92.46%.

Microcrystalline Graphite: Overcoming Closely Intergrown and Entrainment Challenges

Microcrystalline graphite has fine crystals and is closely intergrown with gangue, making it refractory. Conventional processes face difficulties in liberation and flotation entrainment, leading to innovative technologies: selective hydrophobic flocculation flotation (enhancing separation of graphite and gangue through high-shear conditioning, achieving concentrate fixed carbon content up to 95.87%) and cyclonic microbubble flotation column (1 roughing and 3 cleaning stages yielding 88.79% fixed carbon content, with recovery 41.84 percentage points higher than flotation machines), effectively improving separation efficiency.

 Flotation Reagents: Core to Enhancing Separation Efficiency

Flotation reagents regulate mineral surface hydrophobicity and bubble properties to strengthen graphite-impurity separation, mainly including three categories:

Collectors: Non-ionic hydrocarbon oils such as kerosene and diesel are dominant, forming hydrophobic oil films on graphite surfaces to enhance floatability. New reagents like DF (with both collecting and frothing functions) and MB series reduce dosage and improve efficiency; for example, emulsified kerosene significantly enhances flotation of fine graphite particles.

Frothers: Pine oil (2# oil) is commonly used; sec-octanol, with brittle foam and good selectivity, improves recovery. Higher alcohols such as MIBC, widely used abroad, optimize bubble size and stability.

Modifiers: Including depressants (e.g., water glass to depress silicate gangue), pH regulators (e.g., sodium carbonate stabilizing pulp pH at 8-10), and dispersants/flocculants (e.g., sodium hexametaphosphate for slime dispersion, polyacrylamide for fine particle flocculation), regulating pulp environment to enhance separation selectivity.

Outlook

Current graphite beneficiation technologies are relatively mature, but challenges remain, such as flake protection mechanisms, entrainment control of fine gangue, and development of eco-friendly reagents. Future efforts will focus on high-efficiency and environmentally friendly reagent R&D, intelligent equipment application, and integration of beneficiation and purification processes to improve resource utilization and promote high-value utilization of graphite.