Processing Methods for Different Types of Graphite

Graphite is a material that is widely known and used. However, different types of graphite require different processing methods. The main processing methods are as follows:

1. Purification Processing of Graphite Products

Modern graphite processing industries have two main requirements for graphite products:

• High purity large-flake graphite crystals

• Ultra-fine graphite particles (such as particles smaller than 1 μm or 0.5 μm)

Graphite purification and fine powder processing production lines have been established in many graphite processing areas. The main purification method is chemical purification.

The most mature chemical purification process involves melting graphite with caustic alkali at 700°C, followed by washing until neutral. Then hydrochloric acid treatment and further washing are carried out to increase the carbon content of graphite to 98%–99%.

Some manufacturers also use hydrofluoric acid treatment to produce high-purity graphite.

2. Beneficiation and Processing Methods of Crystalline Graphite

Crystalline graphite has good natural floatability, so the flotation method is commonly used for beneficiation.

Since the size of graphite flakes is one of the most important quality indicators, the processing method usually adopts multi-stage grinding and multiple flotation processes to separate large-flake graphite as early as possible.

Common flotation reagents include:

• Collectors: Kerosene, diesel oil, etc.

• Frothers: No. 2 oil, No. 4 oil, etc.

• Regulators: Lime, sodium carbonate

• Depressants: Water glass

These methods help improve graphite quality while maintaining the integrity of graphite flakes.

3. Beneficiation and Processing Methods of Cryptocrystalline Graphite

Cryptocrystalline graphite, also known as microcrystalline graphite, has extremely small crystal particles. The graphite particles are often embedded in clay, making separation difficult.

Due to the high grade of raw ore (generally containing 60%–80% carbon), many graphite mines directly crush and process the extracted ore to produce graphite powder.

Some graphite mines have conducted research on flotation technologies for microcrystalline graphite, such as oil agglomeration flotation, to improve separation efficiency.

Applications of Graphite Electrodes and Graphite Products

Graphite electrodes are widely used in the graphite processing industry. Graphite products retain the excellent properties of natural flake graphite, including:

• Excellent acid resistance

• Strong corrosion resistance

• High temperature resistance up to 3000°C

• Low temperature resistance down to -204°C

• Compressive strength above 800 kg/cm²

• Excellent oxidation resistance

• Strong self-lubricating performance

For example, graphite products have a very low weight loss rate of approximately 1% at 450°C in air, with a rebound rate of 15%–50% (density: 1.1–1.5).

Due to these outstanding properties, graphite products are widely used in:

• Metallurgy

• Chemical industry

• Petrochemical industry

• High-energy physics

• Aerospace

• Electronics

Different Types of Graphite Products

Based on the unique properties of graphite and different engineering requirements, various graphite products have been developed, including:

• High Purity Graphite Products

• Flexible Graphite Products

• Composite Graphite Products

To further improve strength and elasticity, graphite can be combined with:

• Fibers (including synthetic fibers)

• Metal wires

• Metal meshes

• Metal sheets

to produce composite graphite products with enhanced mechanical performance.

Composite graphite products are mainly manufactured by combining graphite with:

• Resins

• Synthetic rubber

• Plastics (such as PTFE, polyethylene, polypropylene, etc.)

through cold pressing or hot bonding processes.

Other graphite products include:

• Liquid Graphite Products (such as graphite emulsions)

• Semi-liquid Graphite Products (such as graphite lubricating grease)