CHEE2945 – Lecture 2
Why is particle size important?:
- An example of where it could be important is in water treatment. A filter can
allow certain small particles through, but not larger ones.
- Particle size is instrumental in the process of froth flotation, where a bubble
rises through a sample of minerals, and the hydrophobic bubbles will attach to
the bubbles and rise to the top. There is an optimal particle size for this
process to occur; 100 – 120 . A huge amount of energy is put into crushing
minerals to this size.
Defining particle size:
- Feret’s diameter is the length between two parallel lines tangential to the
particle.
- Martin’s diameter is the length of a line bisecting two equal areas of the
particle.
- An equivalent perimeter diameter is the diameter of a circle with an equivalent
perimeter length to the particle.
- All the above methods depend on the orientation of the particle when imaged.
Surface area equivalent spherical diameter:
- Surface area can be determined by nitrogen absorption in a vacuum.
- The diameter is defined using a sphere with the same surface area.
dS=
√
S
π
Volume equivalent spherical diameter:
- Volume can be easily measured with Archimedes’ principle.
- The diameter is defined using a sphere with the same volume.
- Sometimes known as a mass equivalent diameter.
dV =
√
3 6V
π
Surface area to volume ratio equivalent spherical diameter:
Why is particle size important?:
- An example of where it could be important is in water treatment. A filter can
allow certain small particles through, but not larger ones.
- Particle size is instrumental in the process of froth flotation, where a bubble
rises through a sample of minerals, and the hydrophobic bubbles will attach to
the bubbles and rise to the top. There is an optimal particle size for this
process to occur; 100 – 120 . A huge amount of energy is put into crushing
minerals to this size.
Defining particle size:
- Feret’s diameter is the length between two parallel lines tangential to the
particle.
- Martin’s diameter is the length of a line bisecting two equal areas of the
particle.
- An equivalent perimeter diameter is the diameter of a circle with an equivalent
perimeter length to the particle.
- All the above methods depend on the orientation of the particle when imaged.
Surface area equivalent spherical diameter:
- Surface area can be determined by nitrogen absorption in a vacuum.
- The diameter is defined using a sphere with the same surface area.
dS=
√
S
π
Volume equivalent spherical diameter:
- Volume can be easily measured with Archimedes’ principle.
- The diameter is defined using a sphere with the same volume.
- Sometimes known as a mass equivalent diameter.
dV =
√
3 6V
π
Surface area to volume ratio equivalent spherical diameter:
