Graphite Processing
Graphite processing methods include flotation, electrical separation, gravity separation, and more. Flotation is the most commonly used method for graphite beneficiation. The separation and classification of graphite ores are primarily suitable for ores with different crystal forms of graphite, as well as ores associated with silicate minerals such as mica or pyrite.
Understanding Graphite
Graphite ore occurs in two forms: amorphous graphite and flaky (or crystalline) graphite. Amorphous graphite is also known as cryptocrystalline graphite. Its crystal structure is small, with a dull, earthy surface, and it has limited industrial applications. However, its raw ore grade is relatively high, typically ranging from 60% to 80%, but its flotation efficiency is poor, and after flotation, its grade does not improve significantly. As a result, ores with a grade lower than 65% are generally not extracted.
Flaky graphite has a layered or leaf-like structure and typically has a lower grade, generally ranging from 3% to 5%. Its highest grade does not exceed 20% to 25%. This type of graphite has good flotation properties, and after flotation, its grade can increase to over 90%. Therefore, ores with a grade of 2% to 3% can also be extracted. Flaky graphite has excellent properties and is commonly used for the production of high-grade carbon products.
For different types of graphite ores, it is crucial not only to assess the ore grade but also to determine the type of graphite to decide on the appropriate processing method.
Processed Graphite Powder
Flotation of Graphite
Flaky graphite has good flotation properties, and most of these ores are processed using flotation. In graphite flotation, kerosene or diesel is typically used as a collector.
Cryptocrystalline graphite ore is often associated with silicate minerals such as mica. During flotation, to suppress these minerals, substances like starch, dextrin, organic adhesives, cellulose, lime, oxidizers, and other agentscan be used.
Process Flowchart
Multi-Stage Grinding and Flotation: To prevent damage to flaky graphite, grinding is typically carried out in several stages. After several stages of regrinding and flotation, the resulting concentrate will have the desired quality.
Combination of Flotation and Gravity Separation: To separate graphite associated with high specific gravity minerals, a combination of gravity separation and flotation is used. In this method, heavy minerals are first separated by gravity, and the tailings containing lighter particles are then subjected to flotation.
Crystalloids Graphite Flotation Flowchart
Graphite ore typically has medium hardness, making it relatively easy to crush. Generally, a three-stage or two-stage open-circuit or a single-stage crushing process is used. The flotation process usually involves a closed-circuit multi-stage grinding and classification system, where materials with medium particle sizes are returned to the beginning of the line for further grinding. There are three forms of multi-stage processes: regrinding of concentrate, regrinding of medium-grade ore, and regrinding of tailings. In the case of crystalline graphite, the regrinding of concentrate process is primarily used, with recovery operations under normal conditions reaching approximately 80%.
Although cryptocrystalline graphite has a high grade, its separation is challenging. Cryptocrystalline graphite has poor flotation properties, and flotation methods can only serve as an initial beneficiation step. In most cases, the ore is manually classified using hand sorting, then crushed and sold.