What Is Particle Size Distribution Analysis?
Within the context of particle science, particle size analysis refers to the determination of the size range and/or the mean size of particles present.
This often refers to a powder sample. This analysis is crucial for both research and commercial applications in a number of different industries and a variety of applications. In the chemical industry, when powders form one or more of the reactants, the exact constitution of the powder is vital to ensure consistency of product. In the construction industry, particularly road building, aggregates must be optimised for maximum strength and durability.
Mining, particularly when semi-autogenous grinding mills are employed, necessitates exact particle analysis to ensure efficient production. Both agriculture and forestry rely on particle counting to prevent contamination and maintain quality.
There are a number of methods for carrying out a particle size analysis and the choice of approach very much depends on the material under investigation and how the result is to be applied. Sieving is one of the most straightforward approaches; using a series of graduated sieves many types of organic and non-organic materials, such as seeds and grain and clays, sands, feldspars and coal, can be analysed.
The limit for dry sieving is usually given as a #100 mesh, which is approximately a 150μm screen and is related to the force required to pass the particle through the mesh. The amount of material in every sieve can be weighed or a microscopic analysis can be carried out to accurately assess the average particle size in each sieve. Sonic sieving and air jet sieving offer more options for finer powders.
Wet sieving also offers options for particles in suspension or prone to agglomeration. Sedimentation, especially zone sedimentation, remains a powerful way to analyse a variety of different materials, both inorganic and organic, with centrifuges and ultracentrifuges employed to apply a centrifugal, separating, force.
Dynamic light scattering can be applied to particles in suspension, or polymers in solution, and relies on the scattering of a monochromatic coherent light source, such as a laser, to give a determination of the particle size distribution (see also particle size distribution analysis). A further optical approach involves dynamic image processing whereby particles flow past a detector to give information about both particle size and shape. A similar approach (acoustic spectroscopy) employs ultrasound for collecting information on dispersed particles in a fluid.