Multotec Group of Companies “Solutions at Work”

Multotec is a leading South African Manufacturer and

Supplier of World Class Industrial Products and Equipment

to the Minerals Processing Industry

All Material and Designs in this presentation are the Proprietary Information of Multotec

Progress Presentation on Kroondal (K1) Milling

Circuit Diagnostic Study

Study Objectives

The main objectives are:

Minimize scats generation

Increase fineness of the product to meet the

envisaged grinds

Increase throughput

Scope

Determine the optimum lifter profile that would

provide the necessary and required mode of

breakages

Determine the optimum top ball size required to

break the top size and the energy required to

achieve target grind for current F80

Scope I: Determination of Optimum

Lifter Profile

Analysis of the current situation

Lifter profile optimization

Current Situation: Mills and operating parameters

Description Primary Ball Mill Secondary Ball Mill

Mill diameter {inside shell} (m) 3.788 5.50

Mill length (m) 5.50 9.08

Mill speed (% of critical) 68/78 74

Mill filling (% of mill volume) 32 34

Top ball size (mm) 80 40

Feed size -30 mm F80-150 um

Total feed rate (t/h) ~169 ~320

Mill power available (kW) 1500 5500

Scope I: Determination of Optimum Lifter

Profile

Primary ball mill installed lifter Secondary ball mill installed lifter

Current Situation: Installed Lifters

Scope I: Determination of Optimum Lifter

Profile

Current Lifter Profile Analysis: Primary Ball Mill

Observations

Increasing mill speed from 68% to 78% resulted in outermost balls impacting at the toe of the

charge

Expected to increase impact breakage needed for the -30 mm feed top size material

The increased energy input would be expected to eliminate the scats

But contrary was observed, more scats were generated instead

Why

Increased mill speed might have resulted in expanded charge; reducing the ball-rock collisions,

Resulted in less selective classification

N68% N78%

Lifters are aggressive for

secondary ball milling

More abrasion and

attrition breakages are

needed for finer feed (F80

of 150 µm)

Current Lifter Profile Analysis: Secondary Ball Mill

Lifter Profile Optimisation

UG2 ore is characterized by weak large rocks and stronger small

rocks

UG2 ore does not require very high energy impacts to break the

large rocks

The increased scats generation was assumed to be the result of

charge expansion (more cataracting) hence more/easy flow of scats

through the charge and less time for it to be milled

Hence aiming at increasing cascading at the same time retaining

some charge cataracting

Balance between achieving study objectives without adversely

affecting lifter life

Considerations

Lifter Optimization: Primary Ball Mill Outermost Balls

Trajectory at 68% Mill Speed

Lifter Optimization: Primary Ball Mill Outermost

Balls Trajectory at 78% Mill Speed

Lifter Optimization: Secondary Ball Mill Outermost

Balls Trajectory at 74% Mill Speed

Lifter Profile Selection for Primary Ball Mill at

68% Mill Speed

Lifter Profile Selection for Primary Ball mill at

78% Mill Speed

Lifter Profile Selection

Width

(mm)

Height

(mm)

Face

Angle

())

H2A

(mm)

Effective

H2A

(mm)

S/H Speed

(%)

Plate

(mm) Calc. Ideal

210 160 20 90 25 1.87 3.1 68 80

165 160 20 90 25 2.35 3.0 68 80

210 160 35 90 25 1.95 4.38 78 80

W:210mm, H2A:90mm,

H:160mm, N68, A:20

W:165mm, H2A:90mm,

H:160mm, N68, A:20 W:210mm, H2A:90mm,

H:160mm, N78, A:35

Lifter Profile Selection for Secondary Ball mill at

74% Mill Speed

Scope II: Determination of

Optimum Top Ball Size and

Energy Requirement

Determination of Optimum Top Ball Size and

Energy Requirement

Determination of top ball size and energy requirement

required:

Characterizing ore Hardness (Bond Ball Mill Work)

Conducted on DMS feed sample

Primary ball mill feed belts cut

Conducting sampling campaign to determine

stream characteristics

Conducted on 30th September 2014

Three cuts collected over 1.5 hours

Samples analyzed for % Solids and Particle Size

Distribution and flow rate for primary Ball mills

feed belts cut

Determination of Optimum Top Ball Size and

Energy Requirement (Cont.)

Sampled points for primary ball mill circuit

PBM Discharge Sump

Primary Mill Feed Bins

DMS fines Settling Cone

2Xdewatering Cyclone

Primary Ball Mill 1

Primary Ball Mill 2

O/s

O/s

Scats

PBM Discharge Sump

Primary Rougher Feed Sump

Determination of Optimum Top Ball Size and

Energy Requirement (Cont.)

Sampled points for Secondary ball mill circuit

Primary Rougher Tails Sump

4Xde-watering Cyclones

Secondary Ball

Trashes

SBM DischargeSump

Secondary Rougher Feed Sump

4Xde-sliming Cyclones

Sec Cleaner Tails

Degrits Sump

Determination of Optimum Top Ball Size and

Energy Requirement

PSD Results Variability

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

0.01 0.1 1 10 100

Cum

Passin

g (

%)

Particle Size (mm)

Particle Size Distribution Plot (PBM 1 Discharge)

PBM1 Discharge (t=0)

PBM1 Discharge (t=30)

PBM1 Discharge (T=60)

PBM1 Discharge (Averages)

Determination of Optimum Top Ball Size and

Energy Requirement

PSD Results Variability

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

0.01 0.1 1 10 100

Cum

Passin

g (

%)

Particle Size (mm)

Particle Size Distribution Plot (PBM 2 Discharge)

PBM2 Discharge (t=0)

PBM2 Discharge (t=30)

PBM2 Discharge (t=60)

PBM2 Discharge (Average)

Determination of Optimum Top Ball Size and

Energy Requirement

PSD Results Variability

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

0.01 0.1 1 10 100

Cum

Passin

g (

%)

Particle Size (mm)

Particle Size Distribution Plot (SBM Discharge)

SBM Discharge (t=0)

SBM Discharge (t=30)

SBM Discharge (t=60)

SBM Discharge (Average)

Determination of Optimum Top Ball Size and

Energy Requirement

Average PSD for each stream was used

Estimation of stream flow rates

Belt feed, DMS feed, DMS product (consisting of sink, DSM

dewatering screen oversize and flash float tails at 22%, 13%

and 65%) and primary rougher feed flow rates were available

Assumptions have to be made in mass balance to obtain

missing stream flow rates:

Calculate settling cone/dewatering cyclone feed based on

flash float tails using DMS product of the day at the day’s

product split

PBM1 & 2 feed obtained from mass balancing using %

solids of U/F and O/F as well as flash float tails % solids

and flow rate assuming 50:50 split of U/F between PBM1

& 2

De-gritting cyclone feed rate from primary rougher tails

No significant mass losses due to leakages

Determination of Top Ball Size

Where:

SG-Ore specific gravity (=3.45, provided)

Wi-Ore Work index (kWh/metric ton) (=14.44 and 18.14 for Belt

cuts and DMS feed samples respectively from BBWI test

conducted)

Di-Mill internal diameter (Inside Shell) (=3.78 m for primary ball mill

and 5.5 m for secondary ball mill)

N-Mill speed as % of critical (=68% and 78% for primary mill and

74% for secondary ball mill)

F80-80% Passing size of the feed from sampling campaign

particle size distribution

K-constant (=350 for Overflow mill)

Top Ball Size Estimates

Description PBM 1 PBM 2 SBM

F80, mm 8.425 10.287

Speed, % 68 78 68

Ball Size

(mm)

75 72 83

Determination of Energy Requirement

Ascertain energy available against energy required for the

current ball mill feed size

Population Balance Model approach was used

Uses plant data (particle size distribution and power) to determine

breakage and selection parameters

Uses the parameters to determine energy required to achieve the

grind for a given feed distribution

Ball Mill Feed Rate

(t/h)

F80 (mm) Current Situation Target

P80 (mm) Power

(kW)

Target grind Power

(kW)

PBM 1 154.2 8.425 0.266 1209 40% -75

um

1671

PBM 2 164.8 10.287 0.296 1008 40% -75

um

1877.9

SBM

Mill Liner Condition Monitoring (PBM1) • Continuous monitoring of liner/lifter profile conducted through

inspection and online Hawkeye system

• Aimed at informing adequate planning and stock management

• Conducted for primary ball mill 1 and secondary ball mill

Date % WEAR AREA REMAINING (Lifter Bars)

MILL SHELL FEED END DISCHARGE END

RING 1 RING 3 RING 6

23/04/2014 100 100 100 100 100

03/07/2014 68 66 93 82

67

01/10/2014 64 47 57 59

61

26/11/2014 38 42 42 33 43

Mill Liner Condition Monitoring (SBM)

Date % WEAR AREA REMAINING (Lifter Bars)

MILL SHELL FEED END DISCHARGE END

RING 1 RING 3 RING 6

01/01/2013 100 100 100

25/02/2014 69 67

03/07/2014 66 50

42

26/11/2014 49 32 33 Relined on 12/11/2014 Relined 26/11/2014

Comments

Primary Ball Mill 1

About 40% of lifter bars wear area remains

This is likely to last for about three months based on the wear

history

Secondary Ball Mill

About 38% of wear area remains for Secondary Ball Mill

This could last for about 8 months based on the wear history

Recommendations

Phase One: Lifter Profile Re-design

Primary ball mill lifter geometry at 68% of critical speed;

Increase the lifter height to angle (H2A) from 80 to 90 mm

Lifter face angle of 20 degrees is suggested

Will results in increased impact breakage needed for the -30 mm

feed top size material without adverse negative effect on cascading

Lifter width of 165 mm instead of 210 mm is suggested

No change to lifter height

The mill speed of 68% of critical speed is recommended as the operation

speed

The lifter width will increase mill volume available

Profile will change load behaviour and ball trajectory

In case the mill speed has to remain at 78% of critical speed, then:

Increase the H2A from 80 to 90 mm

Lifter face angle of 35 degrees is suggested

No changes on lifter width and height

Recommendations (Cont..)

Secondary ball mill lifter geometry

No changes on lifter width

Decrease the lifter H2A from 89 to 68 mm at the current lifter

height of 170 mm

This will increase abrasion and attrition breakage needed for

fine feed (F80 of 150 µm)

Once the lifter profile has been changed, conduct a campaign to

determine the level of improvements achieved before moving to phase

two of improvements

Phase Two

No changes to Top Ball Size is recommended

Increase primary Ball Mill 1 Charge to 35-37% at a mill speed of

68%, noting the modification required to prevent balls escaping out

of the ball mill

Monitor power draw

Multotec Group of Companies “Solutions at Work”

We thank you for the opportunity to make this presentation.

We Wish You a Blessed,

Safe and a Great Festive Season

Thank you