Sometimes worlds collide between mining and the Internet, and in this case, we recently discovered that a popular search term: four types of mineral processing was drawing traffic to our Sepro Knowledge page. In an effort to make sense of this random search term, our mineral processing experts wasted no time digging deeper into what these four types are, why there are four of them and why people were suddenly so interested. VP of R&D and Marketing, Andrew Gillis, breaking down the four types of mineral processing in the video and article below:
Why Four Types?
Further research led Andrew to the Wikipedia page for mineral processing which states, “Mineral processing can involve four general types of unit operation: comminution – particle size reduction; sizing – separation of particle sizes by screening or classification; concentration by taking advantage of physical and surface chemical properties; and dewatering – solid/liquid separation.”
From a practical point of view vs. theoretical, four categories make the most sense. Using our own Mineral Processing 101 paper, Andrew breaks down the theory versus practical reality.
The Importance of Heterogeneity
Revisiting Sepro’s Mineral Processing 101 paper, it was written as a review of the fundamentals of mineral processing. The first principle discussed is heterogeneity, which is about taking a relatively homogenous ore and breaking it into small enough pieces that there are differences amongst the particles. The second principle is exploiting those differences – this is how it ties into the “four types” of mineral processing:
Comminution is the umbrella term for the crushing and grinding processes that create heterogeneity from a homogenous ore, as well as the devices used for comminution: gyratory crushers, jaw crushers, cone crushers, grinding mills, SAG mills, ball mills, high pressure grinding rolls (HPGR). Anything that takes large particles and makes them into small particles falls under the umbrella of comminution – this aligns with the first principle of mineral processing by creating heterogeneity.
In conjunction with comminution, there is usually some type of screening or size separation device used along with comminution equipment. Screens and hydroclones are the two primary types of sizing equipment. These are often necessary in the process of creating heterogeneity because there is often a target particle size necessary to create heterogeneity, for example, 100 microns. Screens and size separation devices can remove particles that are too large and return them back to the comminution equipment to maximize the amount of ore processed to the target size.
Screening and size separation also use the principle of exploiting heterogeneity: screens separate based on differences in size, and hydroclones separate based on both size and density which means they are frequently used to retain gold particles within a grinding circuit.
Concentration is purely a process of exploiting heterogeneity in mineral ores. Physical concentration devices include gravity separators (centrifuges and spirals), magnetic separators, dense media separators and more. These all use physical properties to separate out particles based on differences in specific gravity, magnetism, optical properties, etc. Flotation specifically separates and concentrates based on surface chemical properties.
- Dewatering and Leaching
According to the same Wikipedia article, dewatering is classified as a type of mineral processing despite involving neither of the two fundamental principles of mineral processing. But mines spend a significant amount of time and energy on dewatering with thickeners, filter press, filters, or (if you’re unlucky) thermal drying, so while theoretically it doesn’t make sense to include dewatering as a method of mineral processing, it makes sense from a practical standpoint.
However, the article then states that leaching is not classified as a mineral processing method, but instead should belong under the umbrella of hydrometallurgy. Much like dewatering, leaching is frequently necessary within mineral processing plants, so if dewatering is a type of mineral processing, leaching falls in line for similar reasons.
Learn More About Mineral Processing
Whether there are three, four, or five types of mineral processing depends on whether it’s approached from a theoretical or practical perspective – we hope this article helped guide visitors to our Knowledge repository looking for answers. You can find more detailed papers under our Mineral Systems Knowledge page. For any questions or further information, feel free to reach out to our mineral processing experts by contacting us.