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


5


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


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


� 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


� 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


� 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


� Air flow measurement� Air flow rate

� Temperature

� Static pressure

To Cement Silo

Cement Mill


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


� 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


� Material level in compartment #1 and #2

M

26


� 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


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



3. Sampling within grinding system

4. Evaluation of test

48


� 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


� Air flow measurement� Air flow rate

� Temperature

� Static pressure

To Cement Silo

Cement Mill


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


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:

0

10

20

30

40

50

60

70

80

90

100

1 10 100 1000

% 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”



66

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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Sieve size (um)

Ideal separatorActual separator

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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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Sieve size (um)

Tromp curve

d75

Sharpness = d25/d75•Sharpness = 0.38•Steeper tromp curve, the better the separation

•Ideal separator sharpness = 1

d25

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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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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


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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


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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


•Make sure symmetry feed on rotor �good distribution

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KHD “Sepmaster” and Fuller “O-Sepa”


•Adjust guide vane � good air flow distribution to rotor

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Guide vane


•Check rotor blade condition (wear and deform)� normal classification

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Rotor blade condition


•Upper and Lower seal condition � good classification•Grinding aids � good classification/reduce bypass

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Summary

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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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ball mill optimization

Documents

check air

size reduction

abnormal size

mill drive

psd laser

revise ball

case mill

piece specific