Solids Handling

ZARS Project

Terry Ring

Particle Segregation

Golden Rules of Sampling

• To get a representative sample for analysis– Chemical analysis

– Particle size distribution analysis

• Rule 1 – A powder should be sampled when in motion

• Rule 2– The whole stream of powder should be taken for many

short increments of time in preference to part of the stream being taken for the whole time.

Particle Size

Counting Particles

Histogram Representation Particle Size Distribution

Cumulative Distribution Representation of PSD

Errors in PSD

0

1.0

2.0

Exp

ecte

d E

rror

in %

Errors in PSD

Blending Powders

Classification

• Powder is separated into two streams– Fine Particles– Coarse Particles

• Equipment– Sieves– Cyclones– Centrifuge– Filter– Venturi Scruber– Electrostatic Precipitator

Cyclone

Sieve & Filter Classification

1 10 100 1 1030

0.5

1

Size (microns)

Size

Sel

ectiv

ity

1 10 100 1 1030

0.5

1

Size (microns)

Size

Sel

ectiv

ity

Cyclone Classification

How to Blend Powders

• V- Blender– A in one arm, B in other arm– After 1/2 Turnover

• A/2 & B/2 in center

– After 1 Turns• A/2 & B/2 in each arm

• Is it well mixed??

Segregation

• Particle size distributions should be matched to prevent segregation in a pile of powders

Sedimentation

9

2 2 gRV fst

Laminar Flow

Sedimentation

Dust

• Sedimentation/Diffusion Equilibrium

• Wind velocity prevents settling