How is graphite processed from graphite ore?

After complex industrial processing, the dark graphite ore eventually becomes the "black gold" indispensable to modern industry. This allotrope of carbon is undergoing a transformation from raw ore to precision material.

Graphite flotation process

In the open-pit mine, the graphite ore mined by blasting is loaded into the crusher, and the steel teeth of the jaw crusher crush the ore into 3-5 cm particles. In the drum of the ball mill, the steel balls and the ore continue to collide for 12-24 hours, grinding the material into 0.15 mm fine powder, at which time the graphite flakes begin to peel off from the associated quartz and mica.

The key process in the flotation tank determines the final quality. Kerosene is added to the slurry as a collector and pine oil as a foaming agent, and a foam layer is formed under aeration and stirring. The hydrophobic graphite particles float up with the bubbles, and the hydrophilic gangue minerals sink to the bottom. After 5-7 levels of flotation, the graphite content is increased from 3-8% of the original ore to more than 90%, forming a black satin-like concentrate slurry.

The vacuum filter reduces the moisture content of the concentrate to 18%, and then it enters the rotary drying kiln and tumbles in 300℃ hot air for 4 hours to remove moisture. For high-end applications such as battery negative electrode materials, acid and alkali purification is also required: hydrofluoric acid is used to dissolve silicates, and sodium hydroxide is used to neutralize residual acid to increase the carbon content to more than 99.9%.

Modern processing systems give graphite multiple forms: spherical graphite treated with 3000℃ graphitization is used for lithium batteries, expanded graphite becomes a sealing material, and highly oriented pyrolytic graphite is used in satellite cooling systems. From mines to laboratories, the processing journey of graphite confirms mankind's unremitting pursuit of the limits of materials. This black mineral from deep in the earth's crust is rejuvenating in the field of high-tech.