Particle size distribution
- Abbreviation
- PSD
- Also known as
- PSD, P80
Particle size distribution (PSD) describes the proportions of different particle sizes in a material such as ground ore. In mineral processing it is often summarized as P80, the size through which 80 percent of the material by mass would pass.
What is particle size distribution?
No crushing or grinding process produces particles of a single size. A particle size distribution describes the full range, typically plotted as the cumulative percentage of material, by mass, passing each size.
Single numbers summarize the curve:
- P80: the size through which 80 percent of the product passes. A P80 of 150 micrometers means 80 percent of the material is finer than 150 micrometers.
- F80: the same measure for the feed to a crushing or grinding stage.
- P50 and other percentiles, used where the fine or coarse end matters.
How it is measured
- Sieve analysis, shaking a sample through a stack of screens with progressively smaller openings.
- Laser diffraction, for fine particles.
- Online particle size analyzers, for real-time plant control.
Why it matters in mineral processing
Grinding is typically the most energy-intensive step in a concentrator, and the grind size sets the balance for downstream steps:
- Mineral liberation. Grinding finer frees more valuable mineral from gangue.
- Froth flotation. Very coarse particles can be too heavy to be lifted by bubbles, and very fine particles, or slimes, float slowly and are prone to entrainment, so flotation performance usually peaks over an intermediate size range.
- Dewatering and tailings. Fine particles settle and filter slowly in a thickener or filter.
- Energy and cost. Finer grinding requires much more energy.
Frequently asked questions
No. Finer grinding improves liberation but costs energy and can create slimes that hurt flotation and dewatering. Plants choose a grind that balances these effects.
P80 describes the product of a size-reduction stage. F80 describes its feed. Together they are used in calculating grinding energy.
Sources
- Wills' Mineral Processing Technology, 8th edition, B. A. Wills and J. A. Finch, Butterworth-Heinemann, 2016