comminution (size reduction). special forces outer forces mechanical comminution
TRANSCRIPT
Comminution
(Size reduction)
COMMINUTION
external forces
– smashing– breaking – attrition – pealing – cutting– crushing– other
special forces
– thermal shock– pressure change– bombing with photon and other elemental particles– other
chemical forces
– roztwarzanie– rozpuszczanie– spalanie– bioługowanie– inne
MECHANICAL CHEMICAL
h
a
b
Special forces
Outer forces
Mechanical comminution
a
b
Chemical comminution
biological
acid
Leaching and disssolution
Ways of size reduction
breaking attrition smashing
splitting cutting crunching
Size reduction
CRUSHING dry, + 50 mm
GRINDINGwet, - 50 mm
Types of intergrowths of minerals
regular vein coating oclusion
Methods of separation and optimum particle size in feed
screens (wet)classifiers (wet)hydrocyclones drums jigsshaking tables spiralesconespinched sluiceMozley tablesmagnetic separators (LI*) magnetic separators (HI**)magnetic separators ( HG***) oil agglomertionflotation flocculationDRY SEPARATION screens (dry) air cyclones pneumatic separationair tables magnetic separators (LI*)magnetic separators (HI**)elektrostatic separa tors
1 10 100 1000
particle size in feed, m
0
1 10 100 1000
F < F F = F
FF
F
kr krF << Fkr
rr
s
Splitting of brittle particles
F < F F = Fkr kr
Bending metals
Comminution is a separation process
Feed
Product B
Product A
ordering forces
splitting forces
Feed
modified feed
ordering forces
Indices of comminution
I = degree of reduction = D/d
L = Degree of liberation = L
Mass of free particles of a given component
Mass of a given component in feedL =
Physicomechanical delineation of particle breaking
Er = 0.5G2 V/E + S
Er - breaking energyG - stress at the moment of breakingV - particle volume S - surface area of particle - surface energy of particle E - Young’s modulus
Er = En + Ep + Einne
Er = 0.5G2 V/E + S
Energy of surface formation
Energy of stress formation
Noice, heat, etc.
The Young modulus and surface energy as two principal parameters of comminution.The Young modulus after Lipczyński and co-workers (1984) and www, surface energy after Drzymala (1994)
MaterialYoung modulus
GN/m2 = 109 Pa=GPaSurface energy* mN/m = 10–3 J/m2
Water ~0 72.8
Ice 9.5 (at 268K)*** 90–120
KCl (silvinite) 29.6*6 97(780 °C)
CaF2 (fluorite) 75.8*6 450 (plane 111)
CaCO3 (calcite) 56.5(marble) 230 (100)
Al2O3 ( corundum) 390**** 580 (2050 °C)
C (diamond) 1050-1200** ~3700
Ag 83 923 (995 °C)
Au 78***** 1128 (1120 °C)
Cu 120 1120 (1140 °C)
Pb 16,2 442 (350 °C)
SiO2 50–78 (glass) 230 (1400 °C)
Granite 51.5–61.4 –
Sand stone 34–50 –
Diabase 61–69 –
Empirical delineation of size reduction
dEo = - C dd/df(d) Hukki, 1975
dEo = - C dd/dn
or in a simplified version:
Walker, 1937
dEo - increase of specific (per mass unit) energy of comminution
C - constant
f(d) - function dependent on particle size
dd - change of partcie size
10-04
10-02
1000
1002
1004
1006
1008
particle size d, m
10-03
10-01
1001
1003
1005
1007
1009
En
erg
y co
nsu
mp
tio
n,
Eo
, kW
h/M
ggrinding crushing
f(d) = n = 1
n = 4n = 2
n = 1.5
dE = –Cdd/d f(d)o
Kick
Bond
Rittinger
Specific solutions of the Waker equation
n=1
KK ln(D/d) = Eo = Er/m = Er /V
d - average size of particles after size reduction, m
KK - constant - density of particle, Mg/m3
V - volume of particle, m3
Eo - specific energy of size reduction, J/kgEr - comminution energy, Jm -mass of particle, kg
Kick, 1885
(Energy of comminution is proportional to the volume of the particle)
D - average size of particles before size reduction, m
n=1.5
Eo = KB (1/d0.5 -1/D0.5)
Bond, 1952
i i
i
d
gd
1
i i
i
D
gD
1
(Energy of size reduction depends on both volume and surface area of particle)
Specific solutions of the Waker equation
n =2
Eo = KR (1/d -1/D)
That is Er = KR*(Sd - SD)
S - surface area of particle
Rittinger, 1857
(Comminution energy is proportional to the surface area of particles)
Eo = Er /V
Specific solutions of the Waker equation
10 100 1000
particle size, µm
20
30
40
50
60
70
Fe
con
ten
t in
co
nce
ntr
ate,
%
liberation starting point
full liberation
Comminution equipment: crushers and mills
a b c
d e f
Rys. 3.15. Wybrane urządzenia do rozdrabniania: a – kruszarka walcowa, b – młyn kulowy,c – młyn wah adłowy, d – kruszarka młotkowa, e – łamacz szczękowy, f – kruszarka stożkowaSelected devices for size reduction.a) crushing rolls, b) tumbling mills,
c) pendular mill, d) hammer mill, e) jaw crusher, f) gyratory crusher
http://www.retsch-technology.com/
jaw crusher