classification of solids
Individual solid particles are characterised by their size, shape, and density.
1.1 Particle shape
The shape of an individual particle is expressed in terms of the sphericity F s, which is independent of particle size. The sphericity of a particle is the ratio of the surface-volume ratio of a sphere with equal volume as the particle and the surface-volume ratio of the particle.
For a spherical particle of diameter D p, F s =1; for a non-spherical particle, the sphericity is defined as
Dp: equivalent diameter of particle
Sp: surface area of one particle vp: volume of one particle
The equivalent diameter is sometimes defined as the diameter of a sphere of equal volume. For fine particles,
Dp is usually taken to be the nominal size based on screen analysis or microscopic analysis. The surface area is found from adsorption measurements or from the pressure drop in a bed of particles. For many crushed materials, F s is between 0.6 and 0.8. For particles rounded by abrasion, F s may be as high as 0.95.
1.2 Particle size
In general "diameter" may be specified for any equidimensional particles. Particles that are not equidimensional, i.e. that are longer in one direction than in others, are often characterised by the second longest major dimension. For needle like particles, Dp would refer to the thickness of the particle, not their length. Units used for particle size depend on the size of particles. Coarse particles: inches or millimetres
Fine particles: screen size
Very fine particles: micrometers or nanometers
Ultra fine particles: surface area per unit mass, m2/g
1.3 Mixed particle sizes and size analysis
In a sample of uniform particles of diameter Dp, the total volume of the particles is m/r p, where m = mass of the sample, r p = density. Since the volume of one particle is vp, the total number of particle in the sample is The total surface area of the particles is
To apply the above two equations to mixtures of
particles
1.1 Particle shape
The shape of an individual particle is expressed in terms of the sphericity F s, which is independent of particle size. The sphericity of a particle is the ratio of the surface-volume ratio of a sphere with equal volume as the particle and the surface-volume ratio of the particle.
For a spherical particle of diameter D p, F s =1; for a non-spherical particle, the sphericity is defined as
Dp: equivalent diameter of particle
Sp: surface area of one particle vp: volume of one particle
The equivalent diameter is sometimes defined as the diameter of a sphere of equal volume. For fine particles,
Dp is usually taken to be the nominal size based on screen analysis or microscopic analysis. The surface area is found from adsorption measurements or from the pressure drop in a bed of particles. For many crushed materials, F s is between 0.6 and 0.8. For particles rounded by abrasion, F s may be as high as 0.95.
1.2 Particle size
In general "diameter" may be specified for any equidimensional particles. Particles that are not equidimensional, i.e. that are longer in one direction than in others, are often characterised by the second longest major dimension. For needle like particles, Dp would refer to the thickness of the particle, not their length. Units used for particle size depend on the size of particles. Coarse particles: inches or millimetres
Fine particles: screen size
Very fine particles: micrometers or nanometers
Ultra fine particles: surface area per unit mass, m2/g
1.3 Mixed particle sizes and size analysis
In a sample of uniform particles of diameter Dp, the total volume of the particles is m/r p, where m = mass of the sample, r p = density. Since the volume of one particle is vp, the total number of particle in the sample is The total surface area of the particles is
To apply the above two equations to mixtures of
particles