Particle Characterization

Question 1

flocculation

Answer 1

clumping particles together with the help of a chemical agent (agglomeration with help)

Question 2

leaching

Answer 2

pulling solids out of another solid

Question 3

Application of solids in chemical processes?

Answer 3

petrochemical (cracking of hydrocarbons with solids)
gas phase polymerization
combustion/pyrolysis
mining
pharmaceuticals
agriculture/food

Question 4

Most important characteristics

Answer 4

density, size, size distribution, shape

Question 5

2 general categories of properties

Answer 5

intrinsic, dynamic behaviour (ex. drag coefficient, terminal velocity)

Question 6

Types of particle density

Answer 6

bulk density, particle density (apparent particle density and skeletal density)

Question 7

apparent particle density

Answer 7

used for non-porous particles, density of particles as seen by fluid

Question 8

skeletal density

Answer 8

density of particles excluding pores (if non-porous, equal to apparent density, otherwise greater than apparent density)

Question 9

how to measure skeletal density

Answer 9

crush up particles and then measure, or for non-closed pores, can put in vaccum container and fill with He or N2 and measure amount of injected gas

Question 10

bulk density

Answer 10

density of bulk powder, includes voids between particles

mparticles/Vtotal = density *(1-voidage)

Question 11

Factors affecting bulk density

Answer 11

• particle sphericity (lower voidage = higher density)
• packing method (pressure applied when packing can impact voidage)
• particle size distribution (wide size has smaller particles fit into voidage/smaller monosized particles pack closer together)

Question 12

Sphericity

Answer 12

how spherical a solid is (1 = sphere)

Question 13

How to measure bulk density?

Answer 13

use pictometer (put solid in accurate flask then add liquid until reach a certain volume (10mL), flask volume - liquid volume = particle volume, measure mass of particles for mass then find density!

(need to be aware of packing type: loose, compact, apply pressure (use plunger to standard force))

Question 14

Equivalent diameter

Answer 14

draw cricle around projected area, then get diameter of projected area

**orientation of particle may change projected area

Question 15

Martin’s Diameter

Answer 15

draw a line taht bisects the particle

often called a cord length
**size depends on which line we draw to bisect particle (length can differ)
**often average by taking average of maximum and minimum possible cord length
**also depends on orientation of particle

Question 16

Ferel’s Diameter

Answer 16

draw 2 parallel tagents, distant between is diameter

*orientation of lines may change diameter
**when using method, apply similar points of view for all measured particles

Question 17

Longest dimension diameter

Answer 17

max diameter of Feret’s diameter

Question 18

perimeter diametere

Answer 18

diameter of circle with same circumference as particle

Question 19

Which particle diameter of use?

Answer 19

depends on industry (fluidization typically uses projected area diameter or equivalent diameter)

Question 20

dv (equivalent volume diameter)

Answer 20

diameter of a sphere with the same volume as the particle

Question 21

ds (equivalent surface rea diameter)

Answer 21

diameter of a sphere with the same surface area of the particle

Question 22

dsv (equivalent surface-volume diameter/sauter diameter)

Answer 22

diameter of a sphere with the same surface area to volume ratio as the particle

Question 23

sphericity calcualtion

Answer 23

sphericity = surface area of sphere (with same diameter- volume equivalent diameter)/surface area of particle

Question 24

Sieving

Answer 24

take size in it as average between sieve size and previous sieve size, shake the particles through sieves to find the best location

Question 25

When to use arithemetic average?

Answer 25

if have normal size distribution

Question 26

SEM

Answer 26

use magnets to speed up electron into hitting surface of particles, then expel a surface electron and hits sub electrons which releases x-rays. Use the signals released to reconstruct surface image (external surface morphology), can also get chemical composition for this + crystaline structure (if surface is crystaline)

*specimen must be conducters (insulators accept electrons), can add a thin material coating to insulators to still use this method
**can take 1000x image of a microscope

Question 27

Lazer defraction

Answer 27

put liquid with particles in sample holder (suspect particles with propeller), hit sample with lazer that is refracted. The smaller the particles, the larger the defraction angle

*not good for wide size distributions, small particles hidden behind larger ones
**can also use a gas instead of liquid to carry particles for a dry analysis
**does not give mass % (can get volume and number %)
**only get size distribution, no imaging

Question 28

Electrozne sensing

Answer 28

measure particles in electrolyte
put voltage across electrolyte (measure before and with particles)
as the solids pass through the resistance goes up, so for the same current, the voltage drop would increase

*originally used for blood cells

Question 29

Parameters to visual size distribution

Answer 29

sorting (degree of scatter), skewness (close to bell or shifted to a side), kurtosis (degree of departure from normal, narrow vs flat curve)

*can also use cumulative size distribution

Question 30

Poured Angle of Repose & angle of friction

Answer 30

poured angle of repose = angle that forms when pouring solids down a funnel (measures roughness, larger angle measure more friction)