Download - Ball Mill Optimization
Ball mill optimization
Dhaka, Bangladesh
21 March 2010
1
Introduction
� Mr.PeramasWajananawat
� Experience: 13 Years (2 y in engineering,11 y in production)� Engineering department � Kiln and Burning system
� Siam Cement (Ta Luang) �Kiln system, Raw material grinding and Coal grinding
� Siam Cement (Lampang) � Cement grinding and Packing plant
� The Siam Cement (Thung Song) Co,Ltd
� Production Engineer
� Cement grinding 7 lines
� 2 x Conventional mill 150 t/h (OPC) � KHD
� 2 x Pre-grinding 100 t/h (OPC) � Fuller
� 2 x Semi-finish grinding 270 t/h (OPC) � KHD
� 1 x VRM 120 t/h � Loesche (LM46.2 +2C)
� Cement bag dispatching
� Contact e-mail: [email protected]
2
Contents
1. Objective of Ball mill optimization
2. Mill performance test
3. Air flow and diaphragm
4. Separator performance test
3
Objective
1. Audit performance of grinding system
2. Show the key areas for optimization the ball
mill system
3. Provide the basic information for changes or
modifications within grinding system
4. Reduce power consumption, Quality
improvement or Production improvement
4
Ball mill optimization
5
Ball mill optimization
Mill charge Air flow & Diaphragm Separator
1.Mill sampling test
2.Charge distribution3.Regular top-ups
1.Mill ventilation
2.Water injection3.Diaphragms
1.Tromp curve
2.Separator air flow3.Separator sealing
When: Do optimization
1. In some period (1 month, 1 Quarter, 1 Year or ???)
2. To assess the reason/cause of disturbance
� When abnormal operation
� Poor performance of grinding system
� Low mill output or poor quality product
� High operation or maintenance costs
3. Keep operation in a good efficiency
6
Conventional grinding system
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
Main Machine
1. Feeding system2. Tube mill
3. Dynamic separator4. Dedusting (BF/EP)
5. Transport equip.
7
Mill charge optimization
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
8
What is function of mill?
9
M
Size reduction along the mill-Coarse grinding � 1st compartmentNormal feed size 5% residue 25 mm.Max feed size 0.5% residue 35 mm.-Fine grinding � 2nd compartment
Piece weight (or knocking weight)
� Average weight/piece of grinding
media in each compartment (g/piece)
� Piece weight Impact force
Specific surface
� Average surface area of (ball)
grinding media in each compartment (m2/t)
� Specific surface Attrition force
10
Coarse material grinding Coarse material grinding Fine material grinding Fine material grinding
� Need large ball size
� Need small ball size
�Calculation (for steel ball)
�Piece weight : i = [3.143/6] x d3 x 7.8 ;g/pcs.
�Specific surface : o = 123 / i (1/3) ; m2/ton
Note : d = size of ball (cm)
Ball charge composition
11
Ball charge composition
� Check piece weight and specific surface
Compartment 1
Charge calculation
Fraction Weight, W weight Piece weight, I no., nSpecific surface,
oSurface, O
(mm), d (t) % (g) pcs. (m2/t) (m2)90 5.0 9% 2,989 1,673 8.5 4380 11.0 21% 2,099 5,240 9.6 10670 13.6 26% 1,406 9,671 11.0 14960 15.3 29% 886 17,277 12.8 196
50 5.6 11% 512 10,927 15.4 8640 2.5 5% 262 9,528 19.2 48
Total #1 53.0 100% 976 54,317 11.8 628
Compartment 2
Charge calculation
Fraction Weight, W weight Piece weight, I no., nSpecific surface,
oSurface, O
(mm), d (t) % (g) pcs. (m2/t) (m2)50 0.0 0% 512 0 15.4 0
40 0.0 0% 262 0 19.2 030 5.0 4% 111 45,170 25.6 12825 48.0 35% 64 749,309 30.7 1,476
20 37.5 27% 331,143,35
438.4 1,441
17 46.5 34% 202,308,58
545.2 2,102
Total #1 137.0 100% 324,246,41
737.6 5,147
Piece weight: 976 g/pieceSpecific surface: 11.8 m2/t
Piece weight: 32 g/pieceSpecific surface: 37.6 m2/t
12
Ball charge composition
� General we use (Product Blaine 4,500 cm2/g) for “Conventional”� Cpt.1 : Piece weight 1,500-1,600 g./piece
� Cpt 2 : Specific surface 30-35 m2/t
� For “Pre-grinding system” � “R/P + Conventional”
� Cpt.1: PW ~1,100-1200 g/pc
� Cpt.2: SS ~35-40 m2/t
**depend on product fineness!!
13
Maximum steel ball size (Bond equation)
� B=36 x (F80)1/2 x [(SgxWi)/(100xCsxDe
1/2)]1/3
Where
� B : Maximum ball size (mm.)
� F80 : Feed material size for 80% pass (µm)
� W i : Bond work index (kWh/t)
� Cs : N/Nc (normally ~ 0.7-0.75)
� Sg : Specific gravity of raw material (t/m3)
� De : Effective diameter of mill (m.)
� F80 = log [(0.20) size residue(mm.)
]/log(%residue)
� Example;
Given
• Feed size = 5% res. 25 mm.
• Wi = 13.0 kWh/t
• Cs = 0.7
• Sg = 3.0 t/m3
• De = 4.0 m.
• F80 = log(0.20)25/log(0.05)
• F80 = 13.4 mm.
Find : Maximum ball size
B = 36x(13.4)1/2
x[(3x13)/(100x0.7x41/2
)]1/3
Maximum ball size = 86 mm.
14
Maximum steel ball size
0
20
40
60
80
100
120
140
160
180
2 5 10 15 20 25 30
Max Ball Size (mm.)
Feed Size (mm.), F80
Maximum ball size (mm.) : Clinker Wi 13.0 kWh/t, Cs 0.7, Sg 3
** Typical fresh clinker : 5% residue 25 mm. or F80 = 13.4 mm.
15
Example
� Given• Feed size = 5% res. 20 mm.
• Wi = 12.0 kWh/t
• Cs = 0.7
• Sg = 3.0 t/m3
• De = 2.5 m.
� Find: required maximum ball size
� F80
� Maximum ball size (mm.)
16
Mill performance testSteps
1. Recording of related operational data
2. Air flow measurement
3. Crash stop and visual inspection in mill
4. Sampling in mill
5. Evaluation of test
17
1. Recording of related operational data
� Tube Mill� Feed rate, Return, Grinding aids, Water injection, Mill drive
power (kW)
� Static separator
� Vane position
� Mill ventilation fan� Damper position, Air flow rate (if have instrument), Pressure
� Fan drive power
18
2. Air flow measurement
� Air flow measurement� Air flow rate
� Temperature
� Static pressure
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
19
Mill ventilation air
Mill ventilation air
� Purpose� Forward movement of the material � retention time
� Take out fine particles and so diminish the risk of coating
� Cooling of the material in mill � Diminish coating / dehydration of gypsum
� Usual ranges of ventilation:Air speed in mill
� Open circuit : 0.8 to 1.2 m/sec
� Closed circuit : 1.2 to 1.5 m/sec
20
Mm/sec
**Min 0.5 m/s � tend to result inefficient over grinding and excessive
heat generation with possible coating problem.**Max > 1.4 m/s � drag particle out of mill before they have been sufficiency ground.
�Agglomeration and ball coating
Cause:
�Temperature too high tendency of the
material forming agglomerates/coating on grinding media and liner plates
�Grinding efficiency will be reduce
�Temperature outlet mill range 110-120 C.
21
Test 2
� Mill dimension
� Inside diameter 3 m.
� Degree of filling 28% in both compartment
� Mill ventilation check
� Flow 22,000 m3/h
� Check Air ventilation speed in mill ?
22
Mm/sec
3. Crash stop and visual inspection
� Stable operation before crash stop
� Emergency stop or Crash stop� Tube mill / All auxiliary equipment
� Mill Ventilation
� Disconnect main circuit breaker (Safety !)
� Preparation of sampling equipment (shovel, scoop, plastic bag, meter,
lighting etc.)
23
Preparation of sampling equipment
Lighting Shovel
Scoop
Meter
Meter
Plastic bagLock switch
PPE
Crash stop
24
3. Crash stop and visual inspection
� Visual inspection� Liner and Diaphragm condition � wear, block
� Ball size distribution along the mill � classify liner
� Water spray nozzle condition � clogging
� Foreign material ?
� Ball charge condition � agglomeration, coating
Clogging
Liner
Ball charge
Diaphragm
Clean block slot
25
3. Crash stop and visual inspection
� Material level in compartment #1 and #2
M
26
3. Crash stop and visual inspection
� Ball charge quantity (Filling degree)
� Measurement by free height� Measure average internal diameter, Di
� Measure height, h, in three different points along axis for each grinding compartment
M
Inside diameter, Di
Free height, h
Effective length, L
27
Ball charge quantity (Filling degree)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0.000 0.100 0.200 0.300 0.400 0.500
Degree of filling (%
)
h/De
h
HDe
Meter
Normal range 28-32%
Ball level
h = H- (De/2)
28
4. Sampling inside mill (mill test)
� Sampling of material
� Take ~1 kg sample every 1 m along mill axis
� Each sample collected from 3 point in the same cross section
� Removed some balls and taken sample
� First and last sample in each compartment should be taken from 0.5 m off the wall or diaphragms
1m 0.5 0.50.5 1m 1m 1m 1m 1m 0.51m
1.1
1m 1m
1.2 1.3 1.4 2.1 2.2 2.3 2.4 2.5 2.6 2.71.1 1.2 1.3 1.4
Deep 20 cm.
Take samplingMaterial sampling point in mill
29
1m 0.5 0.50.5 1m 1m 1m 1m 1m 0.51m
1.1
1m 1m
1.2 1.3 1.4 2.1 2.2 2.3 2.4 2.5 2.6 2.71.1 1.2 1.3 1.4
Top view
1
1
1
0.5 m.
2
2
2
3
3
3
4
4
4
5
5
5
6
6
6
7
7
7
8
8
8
9
9
9
10
10
10
11
11
11
0.5 m.
Take 1 sample
•Get total 11 collected
samples along the mill•1 kg per sample
Side view Front view
30
4. Sampling inside mill (mill test) –cont.
� After work inside the mill� Calculation quantity of ball charge and filling degree
� Sample sieve analysis
� 1st compartment ◊ Sieve : 16 , 10 , 6 , 2 , 1.25 , 0.5 , 0.2 mm
� 2nd compartment◊ Sieve : 1.25 , 0.5 , 0.2 , 0.12 , 0.09 , 0.06 mm., Blaine Fineness
� Plot size reduction chart (graph)
31
Sieve test equipment
32
Results: Sieve and Fineness analysis from mill test
Sample Location % residue on sieve (by weight)
Blaine 32 16 8 4 2 1 0.50 0.20 0.09
Position m. cm2/g mm mm mm mm mm mm mm mm mm
Compt 1 pt.1 0.5 7.00 18.00 34.00 47.00 57.00 64.00 71.00 81.00 90.50
1.0 9.00 21.00 36.00 45.00 52.00 60.00 69.00 79.00 89.00
2.0 3.00 7.00 13.00 18.00 20.50 31.00 48.00 67.00 83.00
3.0 0.50 1.00 3.00 5.50 8.00 19.50 29.50 52.00 71.00
pt.2 4.0 0.10 3.00 5.00 7.00 8.00 10.50 22.00 46.00 65.00
pt.3 4.5 0.05 4.00 7.50 9.00 10.50 12.50 28.00 48.50 68.00
Partition **
Compt 2 pt.1 0.5 940 1.00 8.00 32.00 56.00
pt.2 1.0 1080 2.00 9.00 33.00 59.00
2.0 1260 0.50 7.00 24.00 50.00
3.0 1300 0.01 4.00 18.00 42.00
4.0 1500 0.00 1.50 12.00 39.00
5.0 1600 0.00 1.00 9.00 32.00
6.0 1700 0.00 0.50 5.00 27.00
pt.3 7.0 1880 0.00 0.22 4.00 21.00
pt.4 8.0 2000 0.00 0.01 3.00 19.50
9.0 2120 0.00 0.01 1.50 18.50
pt.5 9.5 0.00 0.00 2.00 19.00
33
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
0
10
20
30
40
50
60
70
80
90
100
0.5 1.0 2.0 3.0 4.0 4.5 ** 0.5 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 9.5
Blaine (cm
^2/g)
% Residue on sieve
Length (m.)
Size Reduction Progress32.000 mm
16.000 mm
8.000 mm
4.000 mm
2.000 mm
1.000 mm
0.500 mm
0.200 mm
0.090 mm
Blaine cm2/g
Comp. 1 Comp. 2
0.5 4 4.
5
321 0.
5
4 5321 6 9.5987
0.5 m 0.5 mTypical grinding diagram : OPC 3000 cm2/g
34
5. Evaluation of performance test
� Grinding efficiency� Data for evaluation
� Result from visual inspection inside tube mill
� Sample analysis from longitudinal sampling inside tube mill � Size reduction graph
Cement MillCement Mill
35
Evaluation of mill test � standard reference
� Size reduction along mill axis
� Sieve residues and Blaine value in front of the diaphragms
Compartment
Particle size FLSmidth Holderbank Slegten
First comp.
+0.5 mm. 15-25% 12-25% -
+0.6 mm. 10-20% - -
+1.0 mm. 7-14% - -
+2.0 mm. Max 4% Max 3% Max 5% (at 2.5mm.)
Second comp.
+0.2 mm. 20-30% 20-30% 15-25% (at 0.1mm.)
+0.5 mm. Max 5% Max 5% -
Blaine(cm2/g)
- 2,100 -
36
Evaluation of mill test
Compartment
Particle size
FLSmidth Holderbank
Slegten Mill test Result OK?
First comp.
+0.5 mm. 15-25% 12-25% - 28% Little much
coarse
particle size from
compartment 1
+0.6 mm. 10-20% - - -
+1.0 mm. 7-14% - - 12.5%
+2.0 mm. Max 4% Max 3% Max 5% (at 2.5mm.)
10.5%
Second comp.
+0.2 mm. 20-30% 20-30% 15-25% (at 0.1mm.)
2%
Good!+0.5 mm. Max 5% Max 5% - 0%
Blaine(cm2/g)
- 2,100 - 2,120
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
0
10
20
30
40
50
60
70
80
90
100
0.5 1.0 2.0 3.0 4.0 4.5 ** 0.5 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 9.5
Blaine (cm^2/g)
% Residue on sieve
Length (m.)
Size Reduction Progress32.000 mm
16.000 mm
8.000 mm
4.000 mm
2.000 mm
1.000 mm
0.500 mm
0.200 mm
0.090 mm
Blaine cm2/g
Comp. 1 Comp. 2
37
Evaluation of mill test
� Test result : provide information to� Improvement of ball charge composition
�Maximum ball size and composition
�Charge composition (PW and SS)
� Modification/Replace inside grinding compartment
�Liners
�Diaphragms
� Operation
�Mill ventilation
�Clear diaphragm slot
38
39
Bad condition step liner
Broken liner
Good condition liner
Slot blockage
Inspection
Common problems!
Compartment Result Ball charge Liner/Diaphragm Operation Mill vent.
First comp.
Over limit ofparticle size in
front of diaphragm 1st comp.
-Increase impact force in 1st comp.
-Revise ballcharge and need
larger ball size (piece weight)
-Low lift ingefficiency (visual
inspection)-Clean block at
diaphragm (nib)
-Feed too much(visual
inspection)
-Too high velocity (check air flow)
Second comp.
Over limit ofparticle size in
front of diaphragm 2nd comp.
-Wait for revisecharge in 1st
comp.
-Wait for improve liner in 1st comp.
1st comp. OK but 2nd comp. � over
limit of particle size in front of diaphragm
-Revise ball charge and may
need to increase specific surface or Piece weight
-Check ball charge
distribution along the mill
-Classifier liner efficiency-Clean block at
diaphragm
-Feed too much(visual
inspection)
-Too high velocity (check air flow)
40
Case mill test, CM6 STS (Aug,2008)
1,487
1,626
1,739
1,927
1,807
2,058
2,333 2,314
0
500
1000
1500
2000
2500
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
0 2 4 6 8 10 12 14
5.6 mm. 2 mm. 0.5 mm. 0.212 mm. 0.09 mm. 0.075 mm. 0.045 mm. blaine
Diaphra
gm
Diaphra
gm
% residue
Blain
e (cm
2/g
)
abnormal
41
Evaluate and correction
Compartment
Particle size
FLSmidth Holderba
nkSlegten
Mill test
Result OK?
First comp.
+0.5 mm. 15-25% 12-25% - 31%Abnormal size reduction
(in front of diaphragm),
should clear blockage
diaphragm slot+0.6 mm. 10-20% - - -
+1.0 mm. 7-14% - - -
+2.0 mm. Max 4% Max 3% Max 5%
(at 2.5 mm.)23%
Second comp.
+0.2 mm. 20-30% 20-30% 15-25%
(at 0.1 mm.) 52%Abnormal size reduction
(in front of diaphragm),
should clear blockage
diaphragm slot+0.5 mm. Max 5% Max 5% - 51%
Blaine (cm2/g)
- 2,100 - 2,314
Reference standard
42
Case Mill test from : VDZ congress 2009
43
Cement plant in Europe
• Chamber 1 : good size reduction efficiency• Chamber 2 : 45 micron shown results that grinding has stopped midway through the 2nd chamber
Evaluate and correction
44
• Average ball size in chamber 2 is too small (average 16 mm, PW 17 g.) • Take charge distribution more coarse to increase PW and average ball size diameter (to 42 g. and 22 mm.)
Separator performance test
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
45
What is separator?
46
• Advantage of grinding system with separator
• Reduce the number of fine particle to
be ground in mill• Increase production capacity and
Reduce mill power consumption• Increase % of Active particle in fine
particle of Cement
Advantage of grinding system with separator
47
“Maximized separator performance” � “Maximized power saving”
Separator performance testSteps
1. Recording of related operational data
2. Air flow measurement
3. Sampling within grinding system
4. Evaluation of test
48
1. Recording of related operational data
� Tube Mill� Feed rate, Return, Grinding aids, Water injection, Mill drive
power (kW)
� Dynamic separator
� Rotor speed, Damper/vane position
� Separator drive power (kW)
� Separator circulating fan & Separator ventilation
� Flow rate (if have instrument), Damper position
� Separator fan power (kW)
49
2. Air flow measurement
� Air flow measurement� Air flow rate
� Temperature
� Static pressure
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
Separator circulating air
50
Dynamic Separator circulating air
� Purpose� Distribute and disperse cement dust
� Classify cement dust at rotor
� Take out fine particle from separator to be product
� Usual ranges of circulating airDepend on separator feed and production rate
� Separator load � 1.8-2.5 kg feed / m3
� = Separator feed / Circulating air
� Dust load (fine) � less than 0.75-0.8 kg fine / m3
� = Fine product / Circulating air
Circulating air
flow (m³/h)
Separator feed
(t/h)
Return
Fine product
(t/h)
51
3. Sampling within grinding system
� Operation period � Determined suitable sampling point
� Stable operation
� 6-12 hours duration of performance test
� Taking samples every ~1 hour
52
Sampling plan (stable operation period)
To Cement Silo
Cement Mill
Clinker Gypsum Limestone
Sampling
1
2
3
53
Sampling point in process
Separator feedor mill output
Return (reject) Fine product
Scoop
54
Sampling test
Point Sampling point Weight Required sieve analysis
1 Separator feed � “m” 0.5 kg PSD Laser test, Blaine (cm2/g)
2 Separator return � “g” 0.5 kg PSD Laser test, Blaine (cm2/g)
3 Separator fine � “f” 0.5 kg PSD Laser test, Blaine (cm2/g)
55
PSD analysis equipment
Particle size distribution analysis
56
ThungSong Plant
Result: from “Laser analysis”-Range 1.8-350 um
-Test time <5 mins/sampling
57
Particle Size Distribution (PSD)Rm Rf Rg
Size (um)Feed
%residue
Fines
%residue
Rejects
%residue
1 96.4 95.1 98.1
2 93.9 91.7 96.5
4 89.0 85.3 93.7
8 81.5 74.6 89.9
16 68.8 55.1 85.6
24 60.3 41.2 83.9
32 52.2 28.9 80.9
48 39.4 13.0 71.9
64 32.3 7.4 62.9
96 18.2 0.0 40.5
200 4.9 0.0 11.0
TOTAL: 636.9 492.3 814.9
0
10
20
30
40
50
60
70
80
90
100
1 10 100 1000%
Re
sid
ue
Sieve size (um)
Feed %residue Fines %residue Rejects %residue
58
� Meaning sieve size 32 um� 52.2% of separator feed
residue on sieve size 32 um
� 80.9% of reject residue on sieve size 32 um
Rm Rf Rg
Size (um)Feed
%residue
Fines
%residue
Rejects
%residue
1 96.4 95.1 98.1
2 93.9 91.7 96.5
4 89.0 85.3 93.7
8 81.5 74.6 89.9
16 68.8 55.1 85.6
24 60.3 41.2 83.9
32 52.2 28.9 80.9
48 39.4 13.0 71.9
64 32.3 7.4 62.9
96 18.2 0.0 40.5
200 4.9 0.0 11.0
TOTAL: 636.9 492.3 814.9
59
4. Evaluation of performance test
� Separator efficiency� Data for evaluation
� Particles size analysis of sample within grinding system◊ - Separator feed Rm
◊ - Separator fine Rf
◊ - Separator tailing or Reject Rg
� Tromp curve or Fractional recovery� The tromp curve shows what fraction of particles of different sizes in the
feed material is going in to the coarse fraction (often called Return or Tailing)
� Separator specific loads / Dust Load
60
Tromp curve
� Calculation� Circulation factor (CF)
�CF = (Rf - Rg)/(Rm - Rg)
where
� Rf = % residue on sieve of fine
� Rg = % residue on sieve of coarse
� Rm = % residue on sieve of feed
� In this case (size 48 um)
�Circulation Factor = 1.81
61
Tromp curve
� Calculation� Tromp value
�Tromp (range d1,d2) = [(Rg1-Rg2)/(Rm1-Rm2)]x[1-(1/CF)]x100
where
�Tromp (range d1,d2) : Fraction of particles size between d1 and d2
�Rg = % residue on sieve of coarse (return/reject)
�Rm = % residue on sieve of separator feed
� In this case
�Tromp value (32-48 um) = 31.5%
62
Example� Find Circulation factor (CF) of
particle size 32 um and 48 um� CF = (Rf - Rg)/(Rm - Rg)where
� Rf = % residue on sieve of fine
� Rg = % residue on sieve of coarse
� Rm = % residue on sieve of feed
� Find Tromp value of size in range 32-48 um� Tr (d1,d2)=[(Rg1-Rg2)/(Rm1-Rm2)]x[1-
(1/CF)]x100 where
� Tromp (range d1,d2) : Fraction of particles size
between d1 and d2
� Rg= % residue on sieve of coarse (return/reject)
� Rm = % residue on sieve of separator feed
Rm Rf Rg
Size (um)Feed
%residue
Fines
%residue
Rejects
%residue
1 96.4 95.1 98.1
2 93.9 91.7 96.5
4 89.0 85.3 93.7
8 81.5 74.6 89.9
16 68.8 55.1 85.6
24 60.3 41.2 83.9
32 52.2 28.9 80.9
48 39.4 13.0 71.9
64 32.3 7.4 62.9
96 18.2 0.0 40.5
200 4.9 0.0 11.0
TOTAL: 636.9 492.3 814.9
63
Tromp value meaning “Tromp value (32-48 um) = 31.5%”
For separator feed size between 32-48 um = 100 %“Separator feed”
Separator
31.5% to coarse fraction“Reject/Return”
68.5% to fine fraction“Fine product”
64
Tromp value � Plot “Tromp curve”
65
Rm Rf Rg
Size (um)Feed
%residueFines
%residueRejects %residue
CFSize avg (um)
Tromp value
1 96.4 95.1 98.1 1.76 0.5 22.9
2 93.9 91.7 96.5 1.85 1.5 29.3
4 89.0 85.3 93.7 1.79 3 25.2
8 81.5 74.6 89.9 1.82 6 22.8
16 68.8 55.1 85.6 1.82 12 15.2
24 60.3 41.2 83.9 1.81 20 8.9
32 52.2 28.9 80.9 1.81 28 16.6
48 39.4 13.0 71.9 1.81 40 31.5
64 32.3 7.4 62.9 1.81 56 56.9
96 18.2 0.0 40.5 1.82 80 71.4
200 4.9 0.0 11.0 1.80 148 98.8
TOTAL: 636.9 492.3 814.9 1.81 TOTAL:
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% recovery to return (reject)
Sieve size (um)
Plot “Tromp curve”
Particle size in range 32-48 um-31.5% go to be “Return”-68.5% go to be “Fine product”
Particle size in range 8-16 um-15.2% go to be “Return”-84.8% go to be “Fine product”
Particle size in range 2-4 um-25.2% go to be “Return”-74.8% go to be “Fine product”
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Tromp curve of “Ideal and Actual separator”
Ideal separator
No coarse in product and No fine in return/reject
Actual separator
Have some coarse in product and Have
some fine in return/reject
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1
% recovery to return (reject)
Sieve size (um)
Ideal separatorActual separator
67
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% recovery to return (reject)
Sieve size (um)
Tromp curve
d50
Cut size : d50 = 60 um•The cut size of the separation being made is the particle size where the tromp value is 50% •Meaning : Size 60 um has an equal chance to go either to product or to rejects
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Tromp value meaning � Cut size (d50)
For separator feed size between 48-64 um = 100 %“Separator feed”
Separator
50% to coarse fraction“Reject/Return”
50% to fine fraction“Fine product”
Size ~ 60 um: equal chance to go either to product or to rejects
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% recovery to return (reject)
Sieve size (um)
Tromp curve
d75
Sharpness = d25/d75•Sharpness = 0.38•Steeper tromp curve, the better the separation
•Ideal separator sharpness = 1
d25
70
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% recovery to return (reject)
Sieve size (um)
Tromp curve
Minimum value
Bypass = 8.9%•Meaning : Bypass is an indication of the amount of material that essentially bypasses the separator. •The lower the bypass, the more efficiency the separation.
•3rd generation bypass < 15%
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Evaluation of separator performance test
Item Units Typical range Result Evaluate
Circulation factor - 2-3 1.81 little less
Cut size(d50) microndepend on rotor speed
and fineness level 60 micron seems high
Sharpness (d25/d75) - 0.5 0.38 little less
Bypass % 5-15% 8.90% OK
Separator load kg/m3 1.8-2.5 1.7 OK
Product load kg/m3 0.75 0.6 OK
Action : 1. Increase circulation factor (CF) � Separator load has available
2. Need to increase speed of rotor (due to higher CF � coarser separator feed)
3. Tromp curve move to finer side and d50 change to be less than 60 um.4. Bypass slightly increase5. Power consumption of mill went down.
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% recovery to return (reject)
Sieve size (um)
Improvement Tromp curve
1. Improve product: Reduce cut size
-Increase circulation factor to 2-3-Increase rotor rotation speed-%Bypass may slightly increase � OK
-Check separator load and dust load ?
Result: -Better active particle size of product
-Strength improve
Ideal separatorActual separator
1
73
0
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% recovery to return (reject)
Sieve size (um)
Improvement Tromp curve
2. Improve production rate: Reduce
%bypass -Improve separator feed distribution
-Check separator load and dust load ?-Separator ventilation flow
-Check mechanical seal or leak
-Check guide vane and rotor blade ?
Result: -Increase production rate
-Reduce power consumption
Ideal separatorActual separator
2
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Test result : provide information to :
�Adjustment of separator settings
�Circulation load
�Separating air flow, fan speed ,etc
� Modification inside separator
�Mechanical adjustment ,etc�Mechanical seal
�Dispersion plate
�Guide vane and rotor
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General separator improvement
•Separator feed chuteo 100% feed on dispersion plate (over the rotor) � good distribution
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Feed point and dispersion plate
General separator improvement
•Make sure symmetry feed on rotor �good distribution
77
KHD “Sepmaster” and Fuller “O-Sepa”
General separator improvement
•Adjust guide vane � good air flow distribution to rotor
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Guide vane
General separator improvement
•Check rotor blade condition (wear and deform)� normal classification
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Rotor blade condition
General separator improvement
•Upper and Lower seal condition � good classification•Grinding aids � good classification/reduce bypass
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Summary
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Ball mill optimization
Mill charge Air flow & Diaphragm Separator
1.Mill sampling test
2.Charge distribution3.Regular top-ups
1.Mill ventilation
2.Water injection3.Diaphragms
1.Tromp curve
2.Separator air flow3.Separator sealing
1. Every 6 months
2. Every 1 Year3. 1,000 hours
1. Check and maintain
2. 1,000 hours check3. 1,000 hours check
1. Every 3 months
2. Optimized and maintain3. Every 3 months
Q & A
� Performance test� Mill test and Separator test
� Evaluation
� Visual inspection
� Size reduction graph and Tromp curve
� Improvement
� Charge composition, Operation, ect.
� Results� Energy saving, Quality improvement
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