Transcript Bez tytułu slajdu - Politechnika Wrocławska

Comminution
(Size reduction)
COMMINUTION
MECHANICAL
external forces
– smashing
– breaking
– attrition
– pealing
– cutting
– crushing
– other
CHEMICAL
special forces
– thermal shock
– pressure change
– bombing with
photon and other
elemental particles
– other
chemical forces
– roztwarzanie
– rozpuszczanie
– spalanie
– bioługowanie
– inne
Mechanical comminution
Outer forces
Special forces
Chemical comminution
Leaching and disssolution
acid
biological
Ways of size reduction
smashing
breaking
attrition
splitting
cutting
crunching
CRUSHING
dry, + 50 mm
Size reduction
GRINDING
wet, - 50 mm
Types of intergrowths of minerals
regular
vein
coating
oclusion
Methods of separation and optimum particle size in feed
1
10
100
1000
10
100
1000
screens (wet)
classifiers (wet)
hydrocyclones
drums
jigs
shaking tables
spirales
cones
pinched sluice
Mozley tables
magnetic separators (LI*)
magnetic separators (HI**)
magnetic separators ( HG***)
oil agglomertion
flotation
flocculation
DRY SEPARATION
screens (dry)
air cyclones
pneumatic separation
air tables
magnetic separators (LI*)
magnetic separators (HI**)
elektrostatic separa tors
0
1
particle size in feed,  m
Splitting of brittle particles
F = Fkr
F < Fkr
F << Fkr
Fr
Fr
Fs
Bending metals
F < Fkr
F = Fkr
Comminution is a separation process
Feed
Feed
Product A
ordering
forces
ordering forces
splitting
forces
Product B
modified feed
Indices of comminution
I = degree of reduction = D/d
L = Degree of liberation = eL
Mass of free particles of a given component
eL =
Mass of a given component in feed
Physicomechanical delineation of particle breaking
Noice, heat, etc.
Er = En + Ep + Einne
Energy of stress
formation
Er = 0.5G2 V/E + S
Er - breaking energy
G - stress at the moment of breaking
V - particle volume
S - surface area of particle
 - surface energy of particle
E - Young’s modulus
Energy of surface
formation
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)
Young modulus
GN/m2 = 109 Pa=GPa
Surface energy*
mN/m = 10–3 J/m2
~0
72.8
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)
390****
580 (2050 °C)
1050-1200**
~3700
Ag
83
923 (995 °C)
Au
78*****
1128 (1120 °C)
Cu
120
1120 (1140 °C)
Pb
16,2
442 (350 °C)
50–78 (glass)
230 (1400 °C)
51.5–61.4
–
Sand stone
34–50
–
Diabase
61–69
–
Material
Water
Ice
Al2O3 ( corundum)
C (diamond)
SiO2
Granite
Empirical delineation of size reduction
dEo = - C dd/df(d)
Hukki, 1975
dEo - increase of specific (per mass unit) energy of comminution
C - constant
f(d) - function dependent on particle size
dd - change of partcie size
or in a simplified version:
dEo = - C dd/dn
Walker, 1937
09
grinding
n=
Energy consumption, Eo, kWh/Mg
10
07
10
crushing
4
05
10
n
=
2
03
10
Kick
01
10
n=1
.5
f(d) = n = 1
-01
10
dEo = –Cdd/d
f(d)
-03
10
-04
10
-02
10
00
10
02
10
04
10
particle size d,  m
06
10
08
10
Specific solutions of the Waker equation
n=1
Kick, 1885
KK ln(D/d) = Eo = Er/m = Er /V
d - average size of particles after size reduction, m
D - average size of particles before size reduction, m
KK - constant
 - density of particle, Mg/m3
V - volume of particle, m3
m -mass of particle, kg
Er - comminution energy, J
Eo - specific energy of size reduction, J/kg
(Energy of comminution is proportional to the volume of
the particle)
Specific solutions of the Waker equation
Bond, 1952
n=1.5
Eo = KB (1/d0.5 -1/D0.5)
1
d
gi
i d
i
1
D
gi
i D
i
(Energy of size reduction depends on both volume and
surface area of particle)
Specific solutions of the Waker equation
n =2
Rittinger, 1857
Eo = KR (1/d -1/D)
That is
Eo = Er /V
Er = KR*(Sd - SD)
S - surface area of particle
(Comminution energy is proportional to the surface area
of particles)
70
Fe content in concentrate, %
full liberation
60
50
liberation starting
point
40
30
20
10
100
particle size,  µm
1000
Comminution equipment: crushers and mills
a
b
c
d
e
f
Rys. 3.15. Wybrane urządzenia do rozdrabniania: a – kruszarka walcowa, b – młyn kulowy,
Selected devices
for sizedreduction.a)
crushing
rolls,
b) tumbling
mills,
c – młyn wahadłowy,
– kruszarka młotkowa,
e – łamacz
szczękowy,
f – kruszarka
stożkowa
c) pendular mill, d) hammer mill, e) jaw crusher, f) gyratory crusher
http://www.retsch-technology.com/
jaw crusher
Ball mills
http://ball-mill.fam.de/english/Products
Ball mills
http://ball-mill.fam.de/english/Products
Rod mills
http://ball-mill.fam.de/english/Products
Impact hammer mills
http://ball-mill.fam.de/english/Products
Impact crushers
http://ball-mill.fam.de/english/Products