Why use equivalent particle size in particle size analysis?

The use of equivalent particle size in particle size analysis primarily addresses the challenges of measuring and characterizing irregularly shaped particles. Real particles are extremely complex in morphology (e.g., flakes, needles, porous particles, or rough surfaces) and cannot be directly described by a single geometric dimension (e.g., diameter) like a perfect sphere.

The core idea of equivalent particle size is to equate a certain physical property of an irregular particle to the diameter of an ideal sphere with the same property. The diameter of this ideal sphere is the equivalent particle size of the particle.

1. Unified measurement standard: Provide a unified, quantifiable and comparable standard to simplify the vastly different shapes into a physically meaningful value (diameter).

2. Dependence on the measurement principle: Different particle size analysis techniques (e.g., laser diffraction, sedimentation, and induction) are based on different physical principles (light scattering, sedimentation velocity, and resistance change). These methods essentially measure the equivalent behavior of particles.

3. Correlating particle behavior: Many key behaviors of particles (such as sedimentation velocity, light scattering properties, drag in fluids, reactivity, bulk density, flowability, etc.) are often more closely related to their equivalent particle size than to their true geometric dimensions.

Equivalent particle size is a key bridge between the complex world of irregular particles and the established theories and industrial applications based on spheres. It enables quantitative analysis, comparison, and prediction of the physicochemical behavior of particle systems.